View source for Glossary of engineering: M–Z

{{Short description|List of definitions of terms and concepts commonly used in the study of engineering}}
{{See also|Glossary of engineering: A–L}}
This '''glossary of engineering terms''' is a list of definitions about the major concepts of [[engineering]]. Please see the bottom of the page for glossaries of specific fields of engineering.
{{TopicTOC-Engineering}}
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==M==
{{glossary}}
{{term|term= '''[[Macaulay's method]]'''}}{{defn|defn='''(The double integration method)''' is a technique used in [[structural analysis]] to determine the [[Deflection (engineering)|deflection]] of [[beam theory|Euler-Bernoulli beams]]. Use of Macaulay's technique is very convenient for cases of discontinuous and/or discrete loading. Typically partial uniformly distributed loads (u.d.l.) and uniformly varying loads (u.v.l.) over the span and a number of concentrated loads are conveniently handled using this technique.}}
{{term|term= '''[[Mach number]]'''}}{{defn|defn=The ratio of the speed of an object to the speed of sound.}} 
{{term|term= '''[[Machine]]'''}}{{defn|defn=A machine (or mechanical device) is a [[mechanical structure]] that uses [[Power (physics)|power]] to apply [[force]]s and control [[Motion|movement]] to perform an intended action. Machines can be driven by [[Animal power|animals]] and [[Human power|people]], by natural forces such as [[Wind power|wind]] and [[Water power|water]], and by [[Chemical energy|chemical]], [[Thermal energy|thermal]], or [[electricity|electrical]] power, and include a system of [[mechanism (engineering)|mechanisms]] that shape the actuator input to achieve a specific application of output forces and movement. They can also include [[computers]] and sensors that monitor performance and plan movement, often called [[mechanical system]]s.}}
{{term|term= '''[[Machine code]]'''}}{{defn|defn=In [[computer programming]], machine code, consisting of machine language [[instruction set|instructions]], is a [[low-level programming language]] used to directly control a computer's [[central processing unit]] (CPU). Each instruction causes the CPU to perform a very specific task, such as a load, a store, a [[jump instruction|jump]], or an [[arithmetic logic unit]] (ALU) operation on one or more units of data in the CPU's [[processor register|register]]s or [[CPU cache|memory]].}}
{{term|term= '''[[Machine element]]'''}}{{defn|defn=Or ''hardware'', refers to an elementary component of a [[machine]].  These elements consist of three basic types:
# ''[[Structural element|structural components]]'' such as frame members, [[Bearing (mechanical)|bearings]], [[axle]]s, [[Spline (mechanical)|splines]], [[fastener]]s, [[Seal (mechanical)|seal]]s, and [[lubricant]]s, 
# ''[[Mechanism (engineering)|mechanisms]]'' that [[Motion control|control movement]] in various ways such as [[gear train]]s, [[belt (mechanical)|belt]] or [[chain drive]]s, [[Linkage (mechanical)|linkages]], [[Cam (mechanism)|cam]] and [[cam follower|follower]] systems, including [[brake]]s and [[clutch]]es, and 
# ''[[Control system|control components]]'' such as buttons, switches, indicators, sensors, actuators and computer controllers.<ref>Robert L. Norton, '''Machine Design,''' (4th Edition), Prentice-Hall, 2010</ref>

While generally not considered to be a machine element, the shape, texture and color of covers are an important part of a machine that provide a [[industrial design|styling and operational interface]] between the mechanical components of a machine and its users.

Machine elements are basic mechanical parts and features used as the building blocks of most [[machine]]s.<ref>{{Citation | last1 = Matthews | first1 = Clifford | author2-link = American Society of Mechanical Engineers | last2 = American Society of Mechanical Engineers | title = ASME engineer's data book | page = 249 | publisher = ASME Press | year = 2005 | edition = 2nd | url = https://books.google.com/books?id=dPS2KU0gj-8C&pg=PA249 | isbn = 978-0-7918-0229-8 | postscript =.}}</ref> Most are [[Technical standard|standardized]] to common sizes, but customs are also common for specialized applications.<ref name="bhandari">{{Citation | last = Bhandari | first = V. B. | title = Design of machine elements | page = 10 | publisher = Tata McGraw-Hill | year = 2007 | edition = 2nd | url = https://books.google.com/books?id=d-eNe-VRc1oC&pg=PA10 | isbn = 978-0-07-061141-2 | postscript =.}}</ref> }}
{{term|term= '''[[Machine learning]]'''}}{{defn|defn=(ML), is the study of computer [[algorithm]]s that improve automatically through experience and by the use of data.<ref>{{Cite book|last=Mitchell|first=Tom|url=http://www.cs.cmu.edu/~tom/mlbook.html|title=Machine Learning|publisher=McGraw Hill|year=1997|isbn=0-07-042807-7|location=New York|oclc=36417892|author-link=Tom M. Mitchell}}</ref> It is seen as a part of [[artificial intelligence]]. Machine learning algorithms build a model based on sample data, known as "[[training data]]", in order to make predictions or decisions without being explicitly programmed to do so.{{refn|The definition "without being explicitly programmed" is often attributed to [[Arthur Samuel (computer scientist)|Arthur Samuel]], who coined the term "machine learning" in 1959, but the phrase is not found verbatim in this publication, and may be a [[paraphrase]] that appeared later. Confer "Paraphrasing Arthur Samuel (1959), the question is: How can computers learn to solve problems without being explicitly programmed?" in {{Cite conference|title=Automated Design of Both the Topology and Sizing of Analog Electrical Circuits Using Genetic Programming|conference=Artificial Intelligence in Design '96|last1=Koza|first1=John R.|last2=Bennett|first2=Forrest H.|last3=Andre|first3=David|last4=Keane|first4=Martin A.|date=1996|publisher=Springer, Dordrecht|pages=151–170|language=en|doi=10.1007/978-94-009-0279-4_9}}}} Machine learning algorithms are used in a wide variety of applications, such as in medicine, [[email filtering]], [[speech recognition]], and [[computer vision]], where it is difficult or unfeasible to develop conventional algorithms to perform the needed tasks.<ref name="tvt">Hu, J.; Niu, H.; Carrasco, J.; Lennox, B.; Arvin, F., "[https://ieeexplore.ieee.org/document/9244647 Voronoi-Based Multi-Robot Autonomous Exploration in Unknown Environments via Deep Reinforcement Learning]" IEEE Transactions on Vehicular Technology, 2020.</ref>}}
{{term|term= '''[[Maclaurin series]]'''}}{{defn|defn=In [[mathematics]], the '''Taylor series''' of a [[function (mathematics)|function]] is an [[Series (mathematics)|infinite sum]] of terms that are expressed in terms of the function's [[derivative]]s at a single point. For most common functions, the function and the sum of its Taylor series are equal near this point. Taylor's series are named after [[Brook Taylor]],  who introduced them in 1715.  If zero is the point where the derivatives are considered, a Taylor series is also called a Maclaurin series, after [[Colin Maclaurin]], who made extensive use of this special case of Taylor series in the 18th century.}}
{{term|term= '''[[Magnetic field]]'''}}{{defn|defn=A magnetic field is a [[vector field]] that describes the magnetic influence on moving [[electric charge]]s, [[electric currents]],<ref>{{cite book|last1=Feynman|first1=Richard P.|url=https://feynmanlectures.caltech.edu|title=The Feynman Lectures on Physics|last2=Leighton|first2=Robert B.|last3=Sands|first3=Matthew|date=1963|publisher=[[California Institute of Technology]]|isbn=9780465040858|volume=2}}</ref>{{Rp|ch1}}<ref>{{cite book |last1 = Young |first1 = Hugh D. |last2 = Freedman |first2 = Roger A. |last3 = Ford |first3 = A. Lewis |title = Sears and Zemansky's university physics : with modern physics |publisher = Pearson Addison-Wesley |volume = 2 |date = 2008 |pages = 918–919 |isbn = 9780321501219}}</ref> and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and to the magnetic field.{{Rp|ch13}}<ref>Purcell, Edward. p278. Electricity and Magnetism, 3rd edition, [[Cambridge University Press]], 2013. 839pp.</ref>  A [[permanent magnet]]'s magnetic field pulls on [[ferromagnetic material]]s such as [[iron]], and attracts or repels other magnets.  In addition, a magnetic field that varies with location will exert a force on a range of non-magnetic materials by affecting the motion of their outer atomic electrons. Magnetic fields surround magnetized materials, and are created by electric currents such as those used in [[electromagnet]]s, and by [[electric field]]s varying in time.  Since both strength and direction of a magnetic field may vary with location, they are described as a map assigning a vector to each point of space or, more precisely—because of the way the magnetic field transforms under mirror reflection—as a [[Field (physics)|field]] of [[pseudovector]]s.

In [[electromagnetics]], the term "magnetic field" is used for two distinct but closely related vector fields denoted by the symbols {{math|'''B'''}} and {{math|'''H'''}}. In the [[International System of Units]], {{math|'''H'''}}, magnetic field strength, is measured in the SI base units of [[ampere]] per meter (A/m).<ref>{{SIbrochure9th}}, p. 22</ref> {{math|'''B'''}}, [[magnetic flux]] density, is measured in [[tesla (unit)|tesla]] (in SI base units: kilogram per second<sup>2</sup> per ampere),<ref>{{SIbrochure9th}}, p. 21</ref> which is equivalent to [[newton (unit)|newton]] per meter per ampere. {{math|'''H'''}} and {{math|'''B'''}} differ in how they account for magnetization. In [[vacuum]], the two fields are related through the [[vacuum permeability]], <math>\mathbf{B}/\mu_0 = \mathbf{H}</math>; but in a magnetized material, the terms differ by the material's [[magnetization]] at each point.}}
{{term|term= '''[[Magnetism]]'''}}{{defn|defn=Is a class of physical attributes that are mediated by [[magnetic field]]s. [[Electric current]]s and the [[magnetic moment]]s of elementary particles give rise to a magnetic field, which acts on other currents and magnetic moments. Magnetism is one aspect of the combined phenomenon of [[electromagnetism]]. The most familiar effects occur in [[ferromagnetic]] materials, which are strongly attracted by magnetic fields and can be [[magnetization|magnetized]] to become permanent [[magnet]]s, producing magnetic fields themselves.  Demagnetizing a magnet is also possible.  Only a few substances are ferromagnetic; the most common ones are [[iron]], [[cobalt]] and [[nickel]] and their alloys. The rare-earth metals [[neodymium]] and [[samarium]] are less common examples. The prefix ''{{linktext|ferro-}}'' refers to [[iron]], because permanent magnetism was first observed in [[lodestone]], a form of natural iron ore called [[magnetite]], Fe<sub>3</sub>O<sub>4</sub>.}}
{{term|term= '''[[Manufacturing engineering]]'''}}{{defn|defn=Is a branch of professional [[engineering]] that shares many common concepts and ideas with other fields of engineering such as mechanical, chemical, electrical, and industrial engineering. 
Manufacturing engineering requires the ability to plan the practices of manufacturing; to research and to develop tools, processes, machines and equipment; and to integrate the facilities and systems for producing quality products with the optimum expenditure of capital.<ref>{{Cite book|doi = 10.1007/978-94-011-7038-3_1|title = Handbook of Electronics Manufacturing Engineering|pages = 1–4|year = 1986|last1 = Matisoff|first1 = Bernard S.|isbn = 978-94-011-7040-6|chapter = Manufacturing Engineering: Definition and Purpose}}</ref>

The manufacturing or production engineer's primary focus is to turn raw material into an updated or new product in the most effective, efficient & economic way possible.}}
{{term|term= '''[[Mass balance]]'''}}{{defn|defn=A mass balance, also called a ''material balance'', is an application of [[conservation of mass]] to the analysis of physical systems. By accounting for material entering and leaving a system, [[Mass flow (physics)|mass flow]]s can be identified which might have been unknown, or difficult to measure without this technique.  The exact [[Conservation law (physics)|conservation law]] used in the analysis of the system depends on the context of the problem, but all revolve around mass conservation, i.e., that [[matter]] cannot disappear or be created spontaneously.<ref name="himmelblau">{{cite book | last = Himmelblau | first = David M. | title = Basic Principles and Calculations in Chemical Engineering | edition = 2nd | date = 1967 | publisher = [[Prentice Hall]] | url = http://www.pearsonhighered.com/educator/product/Basic-Principles-and-Calculations-in-Chemical-Engineering/9780132346603.page}}</ref>{{rp|59–62}}}}
{{term|term= '''[[Mass density]]'''}}{{defn|defn=The '''density''' (more precisely, the '''volumetric mass density'''; also known as '''specific mass'''), of a substance is its [[mass]] per unit [[volume]]. The symbol most often used for density is ''ρ'' (the lower case Greek letter [[Rho (letter)|rho]]), although the Latin letter ''D'' can also be used. Mathematically, density is defined as mass divided by volume:<ref>{{cite web | url =http://www.grc.nasa.gov/WWW/BGH/fluden.html | title =Gas Density Glenn research Center | author =''[[National Aeronautic and Space Administration|The National Aeronautic and Atmospheric Administration's]]'' ''[[Glenn Research Center]]'' | publisher =grc.nasa.gov | url-status =dead | archive-url =https://web.archive.org/web/20130414132531/http://www.grc.nasa.gov/WWW/BGH/fluden.html | archive-date =April 14, 2013 | df =mdy-all | access-date =April 9, 2013 }}</ref>

:<math> \rho = \frac{m}{V}</math>

where ''ρ'' is the density, ''m'' is the mass, and ''V'' is the volume. In some cases (for instance, in the United States oil and gas industry), density is loosely defined as its [[weight]] per unit [[volume]],<ref>{{cite web|url=http://oilgasglossary.com/density.html |title=Density definition in Oil Gas Glossary |publisher=Oilgasglossary.com |access-date=September 14, 2010 |url-status=dead |archive-url=https://web.archive.org/web/20100805010226/http://oilgasglossary.com/density.html |archive-date=August 5, 2010 }}</ref> although this is scientifically inaccurate – this quantity is more specifically called [[specific weight]].}}
{{term|term= '''[[Mass moment of inertia]]'''}}{{defn|defn=The '''moment of inertia''', otherwise known as the '''mass moment of inertia''', '''angular mass''', '''second moment of mass''', or most accurately, '''rotational inertia''', of a [[rigid body]] is a quantity that determines the [[torque]] needed for a desired [[angular acceleration]] about a rotational axis, akin to how [[mass]] determines the [[force]] needed for a desired [[acceleration]]. It depends on the body's mass distribution and the axis chosen, with larger moments requiring more torque to change the body's rate of rotation.}}
{{term|term= '''[[Mass number]]'''}}{{defn|defn=The mass number (symbol ''A'', from the German word ''Atomgewicht'' [atomic weight]),<ref>[[Jensen, William B.]] (2005). The Origins of the Symbols A and Z for Atomic Weight and Number. ''J. Chem. Educ.'' 82: 1764. [http://www.che.uc.edu/jensen/W.%20B.%20Jensen/Reprints/123.%20A%20&%20Z.pdf link] {{Webarchive|url=https://web.archive.org/web/20201202054900/http://www.che.uc.edu/jensen/W.%20B.%20Jensen/Reprints/123.%20A%20%26%20Z.pdf |date=2020-12-02 }}.</ref> also called  '''atomic mass number''' or '''nucleon number''', is the total number of [[proton]]s and [[neutron]]s (together known as [[nucleon]]s) in an [[atomic nucleus]]. It is approximately equal to the [[atomic mass|''atomic'' (also known as ''isotopic'') mass]] of the [[atom]] expressed in [[atomic mass unit]]s. Since protons and neutrons are both [[baryon]]s, the mass number ''A'' is identical with the [[baryon number]] ''B'' of the nucleus (and also of the whole atom or [[ion]]). The mass number is different for each different [[isotope]] of a [[chemical element]]. Hence, the difference between the mass number and the [[atomic number]]&nbsp;''Z'' gives the [[Neutron number|number of neutrons]] (''N'') in a given nucleus: {{nowrap|1=''N'' = ''A'' − ''Z''}}.<ref>{{cite web|url=http://education.jlab.org/qa/pen_number.html|title=How many protons, electrons and neutrons are in an atom of krypton, carbon, oxygen, neon, silver, gold, etc...?|publisher=Thomas Jefferson National Accelerator Facility|access-date=2008-08-27}}</ref>

The mass number is written either after the element name or as a [[superscript]] to the left of an element's symbol. For example, the most common isotope of [[carbon]] is [[carbon-12]], or {{SimpleNuclide|carbon|12}}, which has 6 protons and 6 neutrons. The full isotope symbol would also have the atomic number (''Z'') as a subscript to the left of the element symbol directly below the mass number: {{nuclide|carbon|12}}.<ref>{{cite web|url=http://www.fordhamprep.org/gcurran/sho/sho/lessons/lesson35.htm|title=Elemental Notation and Isotopes|publisher=Science Help Online|access-date=2008-08-27|url-status=dead|archive-url=https://web.archive.org/web/20080913063710/http://www.fordhamprep.org/gcurran/sho/sho/lessons/lesson35.htm|archive-date=2008-09-13}}</ref>}}
{{term|term= '''[[Mass spectrometry]]'''}}{{defn|defn=(MS), is an analytical technique that is used to measure the [[mass-to-charge ratio]] of  [[ion]]s. The results are typically presented as a [[mass spectrum]], a plot of intensity as a function of the mass-to-charge ratio. Mass spectrometry is used in many different fields and is applied to pure samples as well as complex mixtures.}}
{{term|term= '''[[Material failure theory]]'''}}{{defn|defn=Is an interdisciplinary field of [[materials science]] and [[solid mechanics]] which attempts to [[Failure analysis|predict the conditions]] under which solid [[material]]s fail under the action of [[Structural load|external loads]]. The failure of a material is usually classified into [[brittle]] failure ([[fracture]]) or [[ductile]] failure ([[yield (engineering)|yield]]). Depending on the conditions (such as [[temperature]], state of [[Stress (mechanics)|stress]], loading rate) most materials can fail in a brittle or ductile manner or both. However, for most practical situations, a material may be classified as either brittle or ductile.

In mathematical terms, failure theory is expressed in the form of various failure criteria which are valid for specific materials.  Failure criteria are functions in [[Stress–strain analysis|stress or strain space]] which separate "failed" states from "unfailed" states.  A precise physical definition of a "failed" state is not easily quantified and several working definitions are in use in the engineering community.  Quite often, phenomenological failure criteria of the same form are used to predict brittle failure and ductile yields.}}
{{term|term= '''[[Material properties]]'''}}{{defn|defn=A materials property is an [[Intensive properties|intensive property]] of some [[chemical change|material]], i.e., a [[physical property]] that does not depend on the amount of the material. These quantitative properties may be used as a [[figure of merit|metric]] by which the benefits of one material versus another can be compared, thereby aiding in [[materials selection]].}}
{{term|term= '''[[Materials science]]'''}}{{defn|defn=The [[Interdisciplinarity|interdisciplinary]] field of materials science, also commonly termed '''materials science and engineering''', covers the design and discovery of new materials, particularly [[solid]]s. The intellectual origins of materials science stem from the [[Age of Enlightenment|Enlightenment]], when researchers began to use analytical thinking from [[chemistry]], [[physics]], and [[engineering]] to understand ancient, [[Empirical relationship|phenomenological]] observations in [[metallurgy]] and [[mineralogy]].<ref>{{cite book|last1= Eddy|first1= Matthew Daniel|title= The Language of Mineralogy: John Walker, Chemistry and the Edinburgh Medical School 1750–1800|date= 2008|publisher= Ashgate|url= https://www.academia.edu/1112014|url-status= live|archive-url= https://web.archive.org/web/20150903230852/http://www.academia.edu/1112014/The_Language_of_Mineralogy_John_Walker_Chemistry_and_the_Edinburgh_Medical_School_1750-1800_2008_|archive-date= 2015-09-03}}</ref><ref name=smith>{{cite book |last= Smith |first= Cyril Stanley |author-link= Cyril Stanley Smith |title= A Search for Structure |date= 1981 |publisher= MIT Press |isbn= 978-0262191913}}</ref> Materials science still incorporates elements of physics, chemistry, and engineering. As such, the field was long considered by academic institutions as a sub-field of these related fields. Beginning in the 1940s, materials science began to be more widely recognized as a specific and distinct field of science and engineering, and major technical universities around the world created dedicated schools for its study.

Materials scientists emphasize understanding, how the history of a material (''processing'') influences its structure, and thus the material's properties and performance. The understanding of processing-structure-properties relationships is called the materials paradigm. This [[paradigm]] is used to advance understanding in a variety of research areas, including [[nanotechnology]], [[biomaterial]]s, and [[metallurgy]].

Materials science is also an important part of [[forensic engineering]] and [[failure analysis]]{{snd}} investigating materials, products, structures or components, which fail or do not function as intended, causing personal injury or damage to property. Such investigations are key to understanding, for example, the causes of various [[aviation accidents and incidents]].}}
{{term|term= '''[[Mathematical optimization]]'''}}{{defn|defn=Mathematical optimization (alternatively spelled ''optimisation'') or '''mathematical programming''' is the selection of a best element, with regard to some criterion, from some set of available alternatives.<ref>"[http://glossary.computing.society.informs.org/index.php?page=nature.html The Nature of Mathematical Programming] {{webarchive|url=https://web.archive.org/web/20140305080324/http://glossary.computing.society.informs.org/index.php?page=nature.html |date=2014-03-05 }}," ''Mathematical Programming Glossary'', INFORMS Computing Society.</ref> Optimization problems of sorts arise in all quantitative disciplines from [[computer science]] and [[engineering]] to [[operations research]] and [[economics]], and the development of solution methods has been of interest in [[mathematics]] for centuries.<ref>{{cite book |last1=Du |first1=D. Z. |last2=Pardalos |first2=P. M. |last3=Wu |first3=W. |year=2008 |chapter=History of Optimization |editor-link=Christodoulos Floudas |editor-last=Floudas |editor-first=C. |editor2-last=Pardalos |editor2-first=P. |title=Encyclopedia of Optimization |publisher=Springer |location=Boston |pages=1538–1542 }}</ref>

In the simplest case, an [[optimization problem]] consists of [[maxima and minima|maximizing or minimizing]] a [[Function of a real variable|real function]] by systematically choosing [[Argument of a function|input]] values from within an allowed set and computing the [[Value (mathematics)|value]] of the function. The generalization of optimization theory and techniques to other formulations constitutes a large area of [[applied mathematics]]. More generally, optimization includes finding "best available" values of some objective function given a defined [[domain of a function|domain]] (or input), including a variety of different types of objective functions and different types of domains.}}
{{term|term= '''[[Mathematical physics]]'''}}{{defn|defn=Refers to the development of [[mathematics|mathematical]] methods for application to problems in [[physics]]. The ''[[Journal of Mathematical Physics]]'' defines the field as "the application of mathematics to problems in physics and the development of mathematical methods suitable for such applications and for the formulation of physical theories".<ref>Definition from the ''Journal of Mathematical Physics''. {{cite web |url=http://jmp.aip.org/jmp/staff.jsp |title=Archived copy |access-date=2006-10-03 |url-status=dead |archive-url=https://web.archive.org/web/20061003233339/http://jmp.aip.org/jmp/staff.jsp |archive-date=2006-10-03 }}</ref>}}
{{term|term= '''[[Mathematics]]'''}}{{defn|defn=Includes the study of such topics as [[quantity]] ([[number theory]]),<ref name="OED">{{cite web |url=http://oed.com/view/Entry/114974 |title=mathematics, ''n.'' |publisher=[[Oxford University Press]] |website=[[Oxford English Dictionary]] |year=2012 |access-date=June 16, 2012 |quote=The science of space, number, quantity, and arrangement, whose methods involve logical reasoning and usually the use of symbolic notation, and which includes geometry, arithmetic, algebra, and analysis. |archive-url=https://web.archive.org/web/20191116075558/https://www.oed.com/view/Entry/114974 |archive-date=November 16, 2019 |url-status=live }}</ref> [[mathematical structure|structure]] ([[algebra]]),<ref name="Kneebone">{{cite book |title=Mathematical Logic and the Foundations of Mathematics: An Introductory Survey |publisher=Dover |author=Kneebone, G.T. |year=1963 |page=[https://books.google.com/books?id=tCXxf4vbXCcC&pg=PA4 4] |isbn=978-0-486-41712-7 |quote=Mathematics&nbsp;... is simply the study of abstract structures, or formal patterns of connectedness.}}</ref> [[space]] ([[geometry]]),<ref name=OED/> and [[calculus|change]] ([[mathematical analysis|analysis]]).<ref name="LaTorre">{{cite book |title=Calculus Concepts: An Informal Approach to the Mathematics of Change |publisher=Cengage Learning |first1=Donald R. |last1=LaTorre |first2=John W. |last2=Kenelly |first3=Sherry S. |last3=Biggers |first4=Laurel R. |last4=Carpenter |first5=Iris B. |last5=Reed |first6=Cynthia R. |last6=Harris |year=2011 |page=[https://books.google.com/books?id=1Ebu2Tij4QsC&pg=PA2 2] |isbn=978-1-4390-4957-0 |quote=Calculus is the study of change—how things change, and how quickly they change.}}</ref><ref name="Ramana">{{cite book |title=Applied Mathematics |publisher=Tata McGraw–Hill Education |author=Ramana |year=2007 |page=[https://books.google.com/books?id=XCRC6BeKhIIC&pg=SA2-PA10 2.10] |isbn=978-0-07-066753-2 |quote=The mathematical study of change, motion, growth or decay is calculus.}}</ref><ref name="Ziegler">{{cite book |title=An Invitation to Mathematics: From Competitions to Research |publisher=Springer |author=Ziegler, Günter M. |author-link=Günter M. Ziegler |year=2011 |page=[https://books.google.com/books?id=9TATfteVeVYC&pg=PR7 vii] |isbn=978-3-642-19532-7 |chapter=What Is Mathematics?}}</ref><!--<<< Please do NOT change the opening sentence without discussion; much time and discussion have been invested in its current form.--> It has no generally accepted [[Definitions of mathematics|definition]].<ref name="Mura">{{cite journal|author=Mura, Roberta|date=Dec 1993|title=Images of Mathematics Held by University Teachers of Mathematical Sciences|journal=Educational Studies in Mathematics|volume=25|issue=4|pages=375–85|doi=10.1007/BF01273907|jstor=3482762|s2cid=122351146}}</ref><ref name="Runge">{{cite book|author1=Tobies, Renate|title=Iris Runge: A Life at the Crossroads of Mathematics, Science, and Industry|title-link=Iris Runge|author2=Helmut Neunzert|publisher=Springer|year=2012|isbn=978-3-0348-0229-1|page=[https://books.google.com/books?id=EDm0eQqFUQ4C&pg=PA9 9]|quote=[I]t is first necessary to ask what is meant by ''mathematics'' in general. Illustrious scholars have debated this matter until they were blue in the face, and yet no consensus has been reached about whether mathematics is a natural science, a branch of the humanities, or an art form.|author1-link=Renate Tobies|name-list-style=amp}}</ref>

[[Mathematicians]] seek and use [[pattern]]s<ref>
 Steen, L.A. (April 29, 1988). The Science of Patterns Science, 240: 611–16. And summarized at Association for Supervision and Curriculum Development [https://web.archive.org/web/20101028101034/http://www.ascd.org/publications/curriculum-handbook/409/chapters/The-Future-of-Mathematics-Education.aspx Archived] October 28, 2010, at the Wayback Machine, www.ascd.org.

</ref><ref>Devlin, Keith, Mathematics: The Science of Patterns: The Search for Order in Life, Mind and the Universe (Scientific American Paperback Library) 1996, ISBN 978-0-7167-5047-5</ref> to formulate new [[conjecture]]s; they resolve the [[truth]] or falsity of such by [[mathematical proof]]. When [[mathematical structure]]s are good models of real phenomena, mathematical reasoning can be used to provide insight or predictions about [[nature]]. Through the use of [[abstraction (mathematics)|abstraction]] and [[logic]], mathematics developed from [[counting]], [[calculation]], [[measurement]], and the systematic study of the [[shape]]s and [[motion (physics)|motions]] of [[physical objects]]. Practical mathematics has been a human activity from as far back as [[History of Mathematics|written records]] exist. The [[research]] required to solve mathematical problems can take years or even centuries of sustained inquiry.}}
{{term|term= '''[[Matrix (mathematics)|Matrix]]'''}}{{defn|defn=In [[mathematics]], a matrix (plural ''matrices'') is a [[rectangle|rectangular]] array or table of [[number]]s, [[symbol (formal)|symbol]]s, or [[expression (mathematics)|expression]]s, arranged in rows and columns, which is used to represent a [[mathematical object]] or a property of such an object. For example, 
:<math>\begin{bmatrix}1 & 9 & -13 \\20 & 5 & -6 \end{bmatrix}</math>
is a matrix with two rows and three columns; one say often a "two by three matrix", a "{{math|2×3}}-matrix", or a matrix of dimension {{math|2×3}}.

Without further specifications, matrices represent [[linear maps]], and allow explicit computations in [[linear algebra]]. Therefore, the study of matrices is a large part of linear algebra, and most properties and [[operation (mathematics)|operations]] of abstract linear algebra can be expressed in terms of matrices. For example, [[matrix multiplication]] represents [[function composition|composition]] of linear maps.

Not all matrices are related to linear algebra. This is in particular the case, in [[graph theory]], of [[incidence matrix|incidence matrices]] and [[adjacency matrix|adjacency matrices]].<ref>However, in the case of adjacency matrices, [[matrix multiplication]] or a variant of it allows the simultaneous computation of the number of paths between any two vertices, and of the shortest length of a path between two vertices.</ref> }}
{{term|term= '''[[Matter]]'''}}{{defn|defn=In [[classical physics]] and general [[chemistry]], matter is any substance that has [[mass]] and takes up space by having [[volume]].<ref name=Penrose/> All everyday objects that can be touched are ultimately composed of [[atom]]s, which are made up of interacting [[subatomic particle]]s, and in everyday as well as scientific usage, "matter" generally includes [[atoms]] and anything made up of them, and any particles (or [[composite particle|combination of particles]]) that act as if they have both [[rest mass]] and volume. However it does not include [[massless particle]]s such as [[photon]]s, or other energy phenomena or waves such as [[light]].<ref name=Penrose >
{{cite book
 |author= R. Penrose
 |date=1991
 |chapter=The mass of the classical vacuum
 |editor1=S. Saunders |editor1-link=Simon Saunders
 |editor2=H.R. Brown |editor2-link=Harvey Brown (philosopher)
 |title=The Philosophy of Vacuum
 |chapter-url=https://books.google.com/books?id=ZU1LL4IbDKcC&pg=PA21
 |pages=21–26
 |publisher=[[Oxford University Press]]
 |isbn=978-0-19-824449-3
 |author-link = Roger Penrose
}}</ref>{{rp|21}}<ref name=mcgrawhill>
{{cite encyclopedia
 |title=Matter (physics)
 |url=http://www.accessscience.com/abstract.aspx?id=410600&referURL=http%3a%2f%2fwww.accessscience.com%2fcontent.aspx%3fid%3d410600
 |encyclopedia=McGraw-Hill's Access Science: Encyclopedia of Science and Technology Online
 |access-date=2009-05-24
 |url-status=dead
 |archive-url=https://web.archive.org/web/20110617073828/http://www.accessscience.com/abstract.aspx?id=410600&referURL=http%3A%2F%2Fwww.accessscience.com%2Fcontent.aspx%3Fid%3D410600
 |archive-date=17 June 2011 }}</ref> Matter exists in various [[state of matter|states]] (also known as [[phase (matter)|phases]]). These include classical everyday phases such as [[solid]], [[liquid]], and [[gas]] – for example [[water]] exists as ice, liquid water, and gaseous steam – but other states are possible, including [[plasma (physics)|plasma]], [[Bose–Einstein condensate]]s, [[fermionic condensate]]s, and [[quark–gluon plasma]].<ref name=RHIC>
{{cite press release
 |date=18 April 2005
 |url=http://www.bnl.gov/bnlweb/pubaf/pr/pr_display.asp?prid=05-38
 |title=RHIC Scientists Serve Up "Perfect" Liquid
 |publisher=[[Brookhaven National Laboratory]]
 |access-date=2009-09-15
}}</ref>}}
{{term|term= '''Maximum-distortion energy theory'''}}{{defn|defn=.}}
{{term|term= '''Maximum-normal-stress theory'''}}{{defn|defn=.}}
{{term|term= '''Maximum shear stress'''}}{{defn|defn=.}}
{{term|term= '''[[Maxwell's equations]]'''}}{{defn|defn=Are a set of coupled [[partial differential equation]]s that, together with the [[Lorentz force]] law, form the foundation of [[classical electromagnetism]], classical [[optics]], and [[electric circuit]]s. 
The equations provide a mathematical model for electric, optical, and radio technologies, such as power generation, electric motors, [[wireless]] communication, lenses, radar etc. They describe how [[electric field|electric]] and [[magnetic field]]s are generated by [[electric charge|charges]], [[electric current|currents]], and changes of the fields.<ref group="note">''Electric'' and ''magnetic'' fields, according to the [[theory of relativity]], are the components of a single electromagnetic field.</ref> The equations are named after the physicist and mathematician [[James Clerk Maxwell]], who, in 1861 and 1862, published an early form of the equations that included the Lorentz force law. Maxwell first used the equations to propose that light is an electromagnetic phenomenon.

An important consequence of Maxwell's equations is that they demonstrate how fluctuating electric and magnetic fields propagate at a constant speed (''[[Speed of light|c]]'') in vacuum. Known as [[electromagnetic radiation]], these waves may occur at various wavelengths to produce a [[Electromagnetic spectrum|spectrum]] of light from [[radio wave]]s to [[gamma ray]]s.}} 
{{term|term= '''[[Mean]]'''}}{{defn|defn=There are several kinds of '''mean''' in [[mathematics]], especially in [[statistics]]:

For a [[data set]], the [[arithmetic mean]], also known as [[average]] or arithmetic average, is a central value of a finite set of numbers: specifically, the sum of the values divided by the number of values. The arithmetic mean of a set of numbers ''x''<sub>1</sub>, ''x''<sub>2</sub>, ..., x''<sub>n</sub>'' is typically denoted by <math>\bar{x}</math>{{refn|Pronounced "''x'' bar".|group="note"}}. If the data set were based on a series of observations obtained by [[sampling (statistics)|sampling]] from a [[statistical population]], the arithmetic mean is the '''sample mean''' (denoted <math>\bar{x}</math>) to distinguish it from the mean, or [[expected value]], of the underlying distribution, the '''population mean''' (denoted '''<math>\mu</math>''' or '''<math>\mu_x</math>'''{{refn|Greek letter [[Mu (letter)|μ]], for "mean", pronounced /'mjuː/.|group="note"}}).<ref>Underhill, L.G.; Bradfield d. (1998) ''Introstat'', Juta and Company Ltd. {{isbn|0-7021-3838-X}} [https://books.google.com/books?id=f6TlVjrSAsgC&pg=PA181 p. 181]</ref>

In [[probability]] and [[statistics]], the '''population mean''', or expected value, is a measure of the [[central tendency]] either of a [[probability distribution]] or of a [[random variable]] characterized by that distribution.<ref>{{cite book|last=Feller|first=William|title=Introduction to Probability Theory and its Applications, Vol I|year=1950|publisher=[[Wiley (publisher)|Wiley]]|isbn=0471257087|pages=221}}</ref> In a [[discrete probability distribution]] of a random variable ''X'', the mean is equal to the sum over every possible value weighted by the probability of that value; that is, it is computed by taking the product of each possible value ''x'' of ''X'' and its probability ''p''(''x''), and then adding all these products together, giving <math>\mu = \sum x p(x)....</math>.<ref>Elementary Statistics by Robert R. Johnson and Patricia J. Kuby, [https://books.google.com/books?id=DWCAh7jWO98C&pg=PA279 p. 279]</ref><ref name=":1">{{Cite web|last=Weisstein|first=Eric W.|title=Population Mean|url=https://mathworld.wolfram.com/PopulationMean.html|access-date=2020-08-21|website=mathworld.wolfram.com|language=en}}</ref> An analogous formula applies to the case of a [[continuous probability distribution]]. Not every probability distribution has a defined mean (see the [[Cauchy distribution]] for an example). Moreover, the mean can be infinite for some distributions.

For a finite population, the '''population mean''' of a property is equal to the arithmetic mean of the given property, while considering every member of the population. For example, the population mean height is equal to the sum of the heights of every individual—divided by the total number of individuals. The sample mean may differ from the population mean, especially for small samples. The [[law of large numbers]] states that the larger the size of the sample, the more likely it is that the sample mean will be close to the population mean.<ref>Schaum's Outline of Theory and Problems of Probability by Seymour Lipschutz and Marc Lipson, [https://books.google.com/books?id=ZKdqlw2ZnAMC&pg=PA141 p. 141]</ref>

Outside probability and statistics, a wide range of other notions of mean are often used in [[geometry]] and [[mathematical analysis]].}}
{{term|term= '''[[Central tendency|Measure of central tendency]]'''}}{{defn|defn=In [[statistics]], a '''central tendency''' (or '''measure of central tendency''') is a central or typical value for a [[probability distribution]].<ref name=Weisberg>Weisberg H.F (1992) ''Central Tendency and Variability'', Sage University Paper Series on Quantitative Applications in the Social Sciences,  {{ISBN|0-8039-4007-6}} p.2</ref> It may also be called a '''center''' or '''location''' of the distribution. Colloquially, measures of central tendency are often called ''[[averages]].'' The term ''central tendency'' dates from the late 1920s.<ref name=Upton/>

The most common measures of central tendency are the [[arithmetic mean]], the [[median]], and the [[Mode (statistics)|mode]].  A middle tendency can be calculated for either a finite set of values or for a theoretical distribution, such as the [[normal distribution]]. Occasionally authors use central tendency to denote "the tendency of quantitative [[data]] to cluster around some central value."<ref name=Upton>Upton, G.; Cook, I. (2008) ''Oxford Dictionary of Statistics'', OUP {{ISBN|978-0-19-954145-4}} (entry for "central tendency")</ref><ref name=Dodge1>Dodge, Y. (2003) ''The Oxford Dictionary of Statistical Terms'', OUP for [[International Statistical Institute]]. {{ISBN|0-19-920613-9}} (entry for "central tendency")</ref>

The central tendency of a distribution is typically contrasted with its ''[[statistical dispersion|dispersion]]'' or ''variability''; dispersion and central tendency are the often characterized properties of distributions. Analysis may judge whether data has a strong or a weak central tendency based on its dispersion.}}
{{term|term= '''[[Mechanical advantage]]'''}}{{defn|defn=Is a measure of the [[force]] amplification achieved by using a tool, [[mechanical device]] or machine system. The device trades off input forces against movement to obtain a desired amplification in the output force.  The model for this is the ''law of the [[lever]].''  Machine components designed to manage forces and movement in this way are called [[mechanism (engineering)|mechanism]]s.<ref name="Uicker">{{cite book | last1=Uicker | first1=John J.| first2=G. R.|last2=Pennock|first3=J. E.|last3=Shigley|title=Theory of machines and mechanisms | publisher=Oxford University Press | publication-place=New York | year=2011 | isbn=978-0-19-537123-9 }}</ref>  
An ideal mechanism transmits power without adding to or subtracting from it.  This means the ideal mechanism does not include a power source, is frictionless, and is constructed from [[rigid bodies]] that do not deflect or wear.  The performance of a real system relative to this ideal is expressed in terms of efficiency factors that take into account departures from the ideal.}}
{{term|term= '''[[Mechanical engineering]]'''}}{{defn|defn=Is an [[engineering]] branch that combines [[engineering physics]] and [[engineering mathematics|mathematics]] principles with [[materials science]] to [[design]], analyze, manufacture, and maintain [[mechanical system]]s.<ref>{{cite web |url=https://me.columbia.edu/what-mechanical-engineering |title= What is Mechanical Engineering?|date= 28 December 2018}}</ref> It is one of the oldest and broadest of the [[List of engineering branches|engineering branches]].}}
{{term|term= '''[[Mechanical filter]]'''}}{{defn|defn=Is a [[filter (signal processing)|signal processing filter]] usually used in place of an [[electronic filter]] at [[radio frequency|radio frequencies]].  Its purpose is the same as that of a normal electronic filter: to pass a range of signal frequencies, but to block others.  The filter acts on mechanical vibrations which are the analogue of the electrical signal.  At the input and output of the filter, [[transducer]]s convert the electrical signal into, and then back from, these mechanical vibrations.}}
{{term|term= '''[[Mechanical wave]]'''}}{{defn|defn=Is a [[wave]] that is an oscillation of [[matter]], and therefore transfers energy through a [[transmission medium|medium]].<ref>Giancoli, D. C. (2009) Physics for scientists & engineers with modern physics (4th ed.). Upper Saddle River, N.J.: Pearson Prentice Hall.</ref> While waves can move over long distances, the movement of the [[transmission medium|medium of transmission]]—the material—is limited. Therefore, the oscillating material does not move far from its initial equilibrium position. Mechanical waves transport energy. This energy propagates in the same direction as the wave. Any kind of wave (mechanical or electromagnetic) has a certain energy. Mechanical waves can be produced only in media which possess [[Elasticity (physics)|elasticity]] and [[inertia]].}}
{{term|term= '''[[Mechanics]]'''}}{{defn|defn=Is the area of [[physics]] concerned with the motions of [[physical object]]s, more specifically the relationships among force, matter, and motion.<ref>{{Cite book|last=Young, Hugh D. (Hugh David), 1930-|url=https://www.worldcat.org/oclc/1104689918|title=Sears and Zemansky's university physics : with modern physics|publisher=|others=Freedman, Roger A., Ford, A. Lewis (Albert Lewis), Estrugo, Katarzyna Zulteta|date=2 September 2019|isbn=978-1-292-31473-0|edition=Fifteenth edition in SI units|location=Harlow|pages=62|oclc=1104689918}}</ref> [[Force]]s applied to objects result in [[Displacement (vector)|displacements]], or changes of an object's position relative to its environment.
This branch of [[physics]] has its origins in [[Ancient Greece]] with the writings of [[Aristotle]] and [[Archimedes]]<ref>Dugas, Rene. A History of Classical Mechanics. New York, NY: [[Dover Publications|Dover Publications Inc]], 1988, pg 19.</ref><ref>Rana, N.C., and Joag, P.S. Classical Mechanics. West Petal Nagar, New Delhi. Tata McGraw-Hill, 1991, pg 6.</ref><ref name="Renn, J. 2010, pg 1-2">Renn, J., Damerow, P., and McLaughlin, P. Aristotle, Archimedes, Euclid, and the Origin of Mechanics: The Perspective of Historical Epistemology. Berlin: Max Planck Institute for the History of Science, 2010, pg 1-2.</ref> (see [[History of classical mechanics]] and [[Timeline of classical mechanics]]). During the [[early modern period]], scientists such as [[Galileo]], [[Johannes Kepler|Kepler]], and [[Isaac Newton|Newton]] laid the foundation for what is now known as [[classical mechanics]].
It is a branch of [[classical physics]] that deals with particles that are either at rest or are moving with velocities significantly less than the speed of light. 
It can also be defined as a branch of science which deals with the motion of and forces on bodies not in the quantum realm. The field is today less widely understood in terms of quantum theory.}}
{{term|term= '''[[Mechanism (engineering)|Mechanism]]'''}}{{defn|defn=Is a [[Machine|device]] that transforms input forces and movement into a desired set of output forces and movement. Mechanisms generally consist of moving components which may include:
* [[Gear]]s and [[gear train]]s;
* [[belt drive|Belts]] and [[chain drive]]s;
* [[Cam (mechanism)|Cam]]s and [[cam follower|follower]]s;
* [[Linkage (mechanical)|Linkages]];
* Friction devices, such as [[brakes]] or [[clutch]]es;
* Structural components such as a frame, fasteners, bearings, springs, or lubricants;
* Various [[machine element]]s, such as splines, pins, or keys.}}
{{term|term= '''[[Median]]'''}}{{defn|defn=In [[statistics]] and [[probability theory]], the median is the value separating the higher half from the lower half of a [[Sample (statistics)|data sample]], a [[statistical population|population]], or a [[probability distribution]]. For a [[data set]], it may be thought of as "the middle" value. The basic feature of the median in describing data compared to the [[Arithmetic mean|mean]] (often simply described as the "average") is that it is not [[Skewness|skewed]] by a small proportion of extremely large or small values, and therefore provides a better representation of a "typical" value. [[Median income]], for example, may be a better way to suggest what a "typical" income is, because income distribution can be very skewed. The median is of central importance in [[robust statistics]], as it is the most [[resistant statistic]], having a [[breakdown point]] of 50%: so long as no more than half the data are contaminated, the median is not an arbitrarily large or small result.}}
{{term|term= '''[[Melting]]'''}}{{defn|defn=Melting, or [[Enthalpy of fusion|fusion]], is a physical process that results in the [[phase transition]] of a [[chemical substance|substance]] from a [[solid]] to a [[liquid]]. This occurs when the [[internal energy]] of the solid increases, typically by the application of [[heat]] or [[pressure]], which increases the substance's [[temperature]] to the [[melting point]]. At the melting point, the ordering of [[ion]]s or [[molecule]]s in the solid breaks down to a less ordered state, and the solid ''melts'' to become a liquid.}}
{{term|term= '''[[Melting point]]'''}}{{defn|defn=The melting point (or, rarely, '''liquefaction point''') of a substance is the [[temperature]] at which it changes [[state of matter|state]] from [[solid]] to [[liquid]]. At the melting point the solid and liquid phase exist in [[Thermodynamic equilibrium|equilibrium]]. The melting point of a substance depends on [[pressure]] and is usually specified at a [[Standard conditions for temperature and pressure|standard pressure]] such as 1 [[Atmosphere (unit)|atmosphere]] or 100 [[Pascal (unit)|kPa]].

When considered as the temperature of the reverse change from liquid to solid, it is referred to as the '''freezing point''' or '''crystallization point'''. Because of the ability of substances to [[Supercooling|supercool]], the freezing point can easily appear to be below its actual value. When the "characteristic freezing point" of a substance is determined, in fact the actual methodology is almost always "the principle of observing the disappearance rather than the formation of ice, that is, the [[#Melting point measurements|melting point]]."<ref>{{cite journal |last1=Ramsay |first1=J. A. |title=A New Method of Freezing-Point Determination for Small Quantities |journal=Journal of Experimental Biology |date=1 May 1949 |volume=26 |issue=1 |pages=57–64 |doi=10.1242/jeb.26.1.57 |pmid=15406812 |url=http://jeb.biologists.org/cgi/pmidlookup?view=long&pmid=15406812 }}</ref>}}
{{term|term= '''[[Meson]]'''}}{{defn|defn=In [[particle physics]], mesons are [[hadron]]ic [[subatomic particle]]s composed of an equal number of [[quarks]] and [[antiquarks]], usually one of each, bound together by [[strong interactions]]. Because mesons are composed of quark subparticles, they have a meaningful physical size, a diameter of roughly one [[femtometer]] (1×10{{sup|−15}}&nbsp;m),<ref>D. Griffiths (2008)</ref> which is about 0.6&nbsp;times the size of a [[proton]] or [[neutron]]. All mesons are unstable, with the longest-lived lasting for only a few hundredths of a microsecond.  Heavier mesons decay to lighter mesons and ultimately to stable [[electron]]s, [[neutrino]]s and [[photon]]s.}}
{{term|term= '''[[Metallic bonding]]'''}}{{defn|defn=Is a type of [[chemical bond]]ing that arises from the electrostatic attractive force between [[conduction electrons]] (in the form of an electron cloud of [[delocalized electron]]s) and positively charged [[metal]] [[ion]]s. It may be described as the sharing of ''free'' electrons among a [[crystal structure|structure]] of positively charged ions ([[cation]]s). Metallic bonding accounts for many [[physical property|physical properties]] of metals, such as [[Strength of materials|strength]], [[ductility]], [[thermal conductivity|thermal]] and [[electrical resistivity and conductivity]], [[Opacity (optics)|opacity]], and [[lustre (mineralogy)|luster]].<ref>[http://www.chemguide.co.uk/atoms/bonding/metallic.html Metallic bonding]. chemguide.co.uk</ref><ref>[http://www.chemguide.co.uk/atoms/structures/metals.html Metal structures]. chemguide.co.uk</ref><ref>[http://hyperphysics.phy-astr.gsu.edu/hbase/chemical/bond.html Chemical Bonds]. chemguide.co.uk</ref><ref>[https://web.archive.org/web/19991018204506/http://www.physics.ohio-state.edu/%7Eaubrecht/physics133.html "Physics 133 Lecture Notes" Spring, 2004. Marion Campus]. physics.ohio-state.edu</ref>

Metallic bonding is not the only type of [[chemical bond]]ing a metal can exhibit, even as a pure substance. For example, elemental [[gallium]] consists of [[covalent bond|covalently-bound]] pairs of atoms in both liquid and solid-state—these pairs form a [[crystal structure]] with metallic bonding between them. Another example of a metal–metal covalent bond is the [[mercurous ion]] ({{chem|Hg|2|2+}}).}}
{{term|term= '''Middle-out'''}} {{defn|defn= A combination of top-down and bottom-up design.<ref>{{cite web |last1=John |first1=Blyler |title=What is middle-out systems engineering? |url=https://www.designnews.com/electronics-test/what-middle-out-systems-engineering |website=DesignNews |access-date=28 September 2020 |date=27 December 2019}}</ref>}}
{{term|term= '''[[Mid-range]]'''}}{{defn|defn=In [[statistics]], the mid-range or ''mid-extreme'' is a measure of [[central tendency]] of a [[sample (statistics)]] defined as the [[arithmetic mean]] of the maximum and minimum values of the [[data set]]:{{sfn|Dodge|2003}}

:<math>M=\frac{\max x + \min x}{2}.</math>

The mid-range is closely related to the [[Range (statistics)|range]], a measure of [[statistical dispersion]] defined as the difference between maximum and minimum values.
The two measures are complementary in sense that if one knows the mid-range and the range, one can find the sample maximum and minimum values.

The mid-range is rarely used in practical statistical analysis, as it lacks [[#Efficiency|efficiency]] as an estimator for most distributions of interest,  because it ignores all intermediate points, and lacks [[#Robustness|robustness]], as outliers change it significantly. Indeed, it is one of the least efficient and least robust statistics. However, it finds some use in special cases: it is the maximally efficient estimator for the center of a uniform distribution, trimmed mid-ranges address robustness, and as an [[L-estimator]], it is simple to understand and compute.}}
{{term|term= '''[[Midhinge]]'''}}{{defn|defn=In [[statistics]], the midhinge is the average of the first and third [[quartile]]s and is thus a measure of [[location parameter|location]].
Equivalently, it is the 25% [[trimmed estimator|trimmed]] [[mid-range]] or 25% [[midsummary]]; it is an [[L-estimator]].

: <math>\operatorname{MH}(X) = \overline{Q_{1, 3}(X)} = \frac{Q_1(X) + Q_3(X)}{2} = \frac{P_{25}(X) + P_{75}(X)}{2} = M_{25}(X)</math>

The midhinge is related to the [[interquartile range]] (IQR), the difference of the third and first [[quartile]]s (i.e. <math>IQR = Q_3 - Q_1</math>), which is a measure of [[statistical dispersion]]. The two are complementary in sense that if one knows the midhinge and the IQR, one can find the first and third quartiles.

The use of the term "hinge" for the lower or upper quartiles derives from [[John Tukey]]'s work on [[exploratory data analysis]] in the late 1970s,<ref>Tukey, J. W. (1977) ''Exploratory Data Analysis'', Addison-Wesley. {{ISBN|0-201-07616-0}}</ref> and "midhinge" is a fairly modern term dating from around that time. The midhinge is slightly simpler to calculate than the [[trimean]] (<math>TM</math>), which originated in the same context and equals the average of the [[median]] (<math>\tilde{X} = Q_2 = P_{50}</math>) and the midhinge.

: <math>\operatorname{MH}(X) = 2 \operatorname{TM}(X) - \operatorname{med}(X) = 2 \frac{Q_1 + 2Q_2 + Q3}{4} - Q_2</math>}}
{{term|term= '''[[Mining engineering]]'''}}{{defn|defn=Mining in the engineering discipline is the extraction of minerals from underneath, above or on the ground. '''Mining engineering''' is associated with many other disciplines, such as [[mineral processing]], exploration, excavation, [[geology]], and [[metallurgy]], [[geotechnical engineering]] and [[surveying]]. A mining engineer may manage any phase of mining operations, from exploration and discovery of the mineral resources, through [[feasibility study]], mine design, development of plans, [[production (economics)|production]] and operations to [[mine closure]].}}
{{term|term= '''[[Miller indices]]'''}}{{defn|defn=Miller indices form a notation system in [[crystallography]] for planes in [[Bravais lattice|crystal (Bravais) lattices]].

In particular, a family of [[lattice plane]]s is determined by three [[integer]]s ''h'', ''k'', and&nbsp;''ℓ'', the ''Miller indices''.  They are written (hkℓ), and denote the family of planes orthogonal to <math>h\mathbf{b_1} + k\mathbf{b_2} + \ell\mathbf{b_3}</math>, where <math>\mathbf{b_i}</math> are the [[Basis (linear algebra)|basis]] of the [[reciprocal lattice]] vectors (note that the plane is not always orthogonal to the linear combination of direct lattice vectors <math>h\mathbf{a_1} + k\mathbf{a_2} + \ell\mathbf{a_3}</math> because the  lattice vectors need not be mutually orthogonal). By convention, [[negative integer]]s are written with a bar, as in {{overline|3}} for&nbsp;−3.  The integers are usually written in lowest terms, i.e. their [[greatest common divisor]] should be&nbsp;1. Miller indices are also used to designate reflections in [[X-ray crystallography]]. In this case the integers are not necessarily in lowest terms, and can be thought of as corresponding to planes spaced such that the reflections from adjacent planes would have a phase difference of exactly one wavelength (2π), regardless of whether there are atoms on all these planes or not.

There are also several related notations:<ref name="Ash">{{Cite book|url=https://archive.org/details/solidstatephysic00ashc|title=Solid state physics|last1=Ashcroft|first1=Neil W.|date=1976|publisher=Holt, Rinehart and Winston|last2=Mermin|first2=N. David|isbn=0030839939|location=New York|oclc=934604|url-access=registration}}</ref>
*the notation {hkℓ} denotes the set of all planes that are equivalent to (hkℓ) by the symmetry of the lattice.
In the context of crystal ''directions'' (not planes), the corresponding notations are:
*[hkℓ], with square instead of round brackets, denotes a direction in the basis of the ''direct'' lattice vectors instead of the reciprocal lattice; and
*similarly, the notation <hkℓ> denotes the set of all directions that are equivalent to [hkℓ] by symmetry.}}
{{term|term= '''[[Mobile robot]]'''}}{{defn|defn=Is a [[robot]] that is capable of moving in the surrounding (locomotion).<ref name="tvt2">Hu, J.; Bhowmick, P.; Lanzon, A., "[https://ieeexplore.ieee.org/document/9468402 Group Coordinated Control of Networked Mobile Robots with Applications to Object Transportation]" IEEE Transactions on Vehicular Technology, 2021.</ref> Mobile robotics is usually considered to be a subfield of [[robotics]] and [[Information engineering (field)|information engineering]].<ref>{{Cite web|url=http://www.robots.ox.ac.uk/|title=Information Engineering Main/Home Page|website=www.robots.ox.ac.uk|language=en|access-date=2018-10-03}}</ref>

Mobile robots have the capability to move around in their environment and are not fixed to one physical location.  Mobile robots can be "autonomous" (AMR - [[autonomous mobile robot]]) which means they are capable of navigating an uncontrolled environment without the need for physical or electro-mechanical guidance devices.<ref name="tro">Hu, J.; Bhowmick, P.; Jang, I.;  Arvin, F.; Lanzon, A., "[https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=9423979 A Decentralized Cluster Formation Containment Framework for Multirobot Systems]" IEEE Transactions on Robotics, 2021.</ref>  Alternatively, mobile robots can rely on guidance devices that allow them to travel a pre-defined navigation route in relatively controlled space.<ref name="tcas">Hu, J.; Turgut, A.; Lennox, B.; Arvin, F., "[https://ieeexplore.ieee.org/abstract/document/9409965 Robust Formation Coordination of Robot Swarms with Nonlinear Dynamics and Unknown Disturbances: Design and Experiments]" IEEE Transactions on Circuits and Systems II: Express Briefs, 2021.</ref>  By contrast, [[industrial robots]] are usually more-or-less stationary, consisting of a [[jointed arm]] (multi-linked manipulator) and [[Robot end effector|gripper]] assembly (or [[Robot end effector|end effector]]), attached to a fixed surface. The joint-arm are controlled by linear actuator or servo motor or stepper motor.}}
{{term|term= '''[[Mode (statistics)|Mode]]'''}}{{defn|defn=The mode is the value that appears most often in a set of data values.<ref>[[Damodar N. Gujarati]]. ''Essentials of Econometrics''. McGraw-Hill Irwin. 3rd edition, 2006: p. 110.</ref> If {{mvar|'''X'''}} is a discrete random variable, the mode is the value {{mvar|x}}  (i.e., {{math|'''''X''''' {{=}} ''x''}}) at which the  [[probability mass function]] takes its maximum value. In other words, it is the value that is most likely to be sampled.

Like the statistical [[mean]] and [[median]], the mode is a way of expressing, in a (usually) single number, important information about a [[random variable]] or a [[population (statistics)|population]]. The numerical value of the mode is the same as that of the mean and median in a [[normal distribution]], and it may be very different in highly [[skewed distribution]]s.}}
{{term|term= '''[[Modulus of elasticity]]'''}}{{defn|defn=An '''elastic modulus''' (also known as '''modulus of elasticity''') is a quantity that measures an object or substance's resistance to being deformed elastically (i.e., non-permanently) when a [[Stress (mechanics)|stress]] is applied to it. The elastic modulus of an object is defined as the [[slope]] of its [[stress–strain curve]] in the elastic deformation region:<ref>{{cite book| last1 = Askeland| first1 = Donald R.| last2 = Phulé| first2 = Pradeep P.| title = The science and engineering of materials| year = 2006| publisher = Cengage Learning| page = 198| edition = 5th| url = https://books.google.com/books?id=fRbZslUtpBYC&pg=PA198| isbn = 978-0-534-55396-8}}</ref> A stiffer material will have a higher elastic modulus. An elastic modulus has the form:

:<math>\delta \ \stackrel{\text{def}}{=}\  \frac {\text{stress}} {\text{strain}}</math>

where <var>[[stress (physics)|stress]]</var> is the force causing the deformation divided by the area to which the force is applied and <var>[[strain (materials science)|strain]]</var> is the ratio of the change in some parameter caused by the deformation to the original value of the parameter. Since strain is a dimensionless quantity, the units of <math>\delta</math> will be the same as the units of stress.<ref>{{cite book | last1 = Beer | first1 = Ferdinand P. | last2 = Johnston | first2 = E. Russell | last3 = Dewolf | first3 = John | last4 = Mazurek | first4 = David | title = Mechanics of Materials | url = https://archive.org/details/mechanicsmateria00beer_274 | url-access = limited | year = 2009 | publisher = McGraw Hill | page = [https://archive.org/details/mechanicsmateria00beer_274/page/n78 56] | isbn = 978-0-07-015389-9}}</ref>}}
{{term|term= '''[[Mohr's circle]]'''}} {{defn|defn= A graphical method of analyzing the three-dimensional stresses in  a system that has a loading force applied to it.}}
{{term|term= '''[[Molality]]'''}}{{defn|defn=Is a measure of the number of moles of solute in a solution corresponding to 1&nbsp;kg or 1000 g of solvent. This contrasts with the definition of [[molarity]] which is based on a specified [[volume]] of solution.

A commonly used unit for molality in [[chemistry]] is [[Mole (unit)|mol]]/[[kilogram|kg]]. A solution of concentration 1&nbsp;mol/kg is also sometimes denoted as ''1 molal''. The unit ''mol/kg'' requires that molar mass be expressed in ''kg/mol'', instead of the usual ''g/mol'' or ''kg/kmol''.}}

{{term|term= '''[[Molar attenuation coefficient]]'''}}{{defn|defn=Is a measurement of how strongly a [[chemical species]] attenuates light at a given [[wavelength]]. It is an [[intrinsic property]] of the species. The [[International System of Units|SI unit]] of molar attenuation coefficient is the square metre per [[Mole (unit)|mole]] ({{nowrap|m<sup>2</sup>/mol}}), but in practice, quantities are usually expressed in terms of [[Molar concentration#Units|<span title="mol/L">M</span>]]<sup>−1</sup>⋅cm<sup>−1</sup> or L⋅mol<sup>−1</sup>⋅cm<sup>−1</sup> (the latter two units are both equal to {{nowrap|0.1 m<sup>2</sup>/mol}}). In older literature, the cm<sup>2</sup>/mol is sometimes used; 1 M<sup>−1</sup>⋅cm<sup>−1</sup> equals 1000 cm<sup>2</sup>/mol. The molar attenuation coefficient is also known as the '''molar extinction coefficient''' and '''molar absorptivity''', but the use of these alternative terms has been discouraged by the IUPAC.<ref>{{GoldBookRef|title=Extinction|file=E02293|accessdate=2015-03-15}}</ref><ref>{{GoldBookRef|title=Absorptivity|file=A00044|accessdate=2015-03-15}}</ref>}}

{{term|term= '''[[Molar concentration]]'''}}{{defn|defn=Molar concentration (also called '''molarity''', '''amount concentration''' or '''substance concentration''') is a measure of the [[concentration]] of a [[chemical species]], in particular of a [[solute]] in a [[Solution (chemistry)|solution]], in terms of [[amount of substance]] per unit [[volume]] of solution. In [[chemistry]], the most commonly used unit for molarity is the number of [[Mole (unit)|moles]] per [[liter]], having the unit symbol mol/L or [[Mole (unit)|mol]]⋅[[Decimetre|dm]]<sup>−3</sup> in SI unit. A solution with a concentration of 1&nbsp;mol/L is said to be 1&nbsp;molar, commonly designated as 1&nbsp;M. To avoid confusion with [[SI prefix]] [[Mega-|mega]], which has the same abbreviation, [[small caps]] [[:wikt:ᴍ|ᴍ]] or [[italicized]] ''M'' are also used in journals and textbooks.<ref>{{cite web |url=https://tex.stackexchange.com/questions/191114/typography-of-unit-symbols-for-molar-and-liter-in-siunitx |title=Typography of unit symbols for Molar and Liter in siunitx |website=TeX - LaTeX Stack Exchange}}</ref>}}
{{term|term= '''[[Molar mass]]'''}}{{defn|defn=In [[chemistry]], the molar mass of a [[chemical compound]] is defined as the [[mass]] of a sample of that compound divided by the [[amount of substance]] in that sample, measured in [[mole (unit)|moles]].<ref name="GreenBook">{{GreenBookRef|page=41}}</ref> It is the mass of 1&nbsp;mole of the substance or {{val|6.022|e=23}} particles, expressed in grams.  The molar mass is a bulk, not molecular, property of a substance. The molar mass is an ''average'' of many instances of the compound, which often vary in mass due to the presence of [[isotope]]s. Most commonly, the molar mass is computed from the [[standard atomic weight]]s and is thus a terrestrial average and a function of the relative abundance of the isotopes of the constituent atoms on Earth. The molar mass is appropriate for converting between the mass of a substance and the amount of a substance for bulk quantities.}}
{{term|term= '''[[Molding (process)|Molding]]'''}}{{defn|defn=Molding ([[American English]]) or '''moulding''' ([[British English|British]] and [[Commonwealth English]]; see [[American and British English spelling differences|spelling differences]]) is the process of [[manufacturing]] by shaping liquid or pliable raw material using a rigid frame called a mold or matrix.<ref>{{cite web|url=http://www.merriam-webster.com/dictionary/molding|title=Molding – Definition of molding by Merriam-Webster|work=merriam-webster.com|date=26 June 2023 }}</ref> This itself may have been made using a pattern or model of the final object.}}
{{term|term= '''[[Molecule]]'''}}{{defn|defn=A molecule is an [[electrically]] neutral group of two or more [[atom]]s held together by [[chemical bond]]s.<ref name="iupac">{{GoldBookRef| title=Molecule|file=M04002|accessdate=23 February 2016}}</ref><ref>{{cite book| author= Ebbin, Darrell D.| title= General Chemistry |edition=3rd| date= 1990| publisher= [[Houghton Mifflin Co.]]| location= Boston| isbn= 978-0-395-43302-7}}</ref><ref>{{cite book| author= Brown, T.L. |author2=Kenneth C. Kemp |author3=Theodore L. Brown |author4=Harold Eugene LeMay |author5=Bruce Edward Bursten |title= Chemistry – the Central Science | url= https://archive.org/details/studentlectureno00theo | url-access= registration |edition=9th| date= 2003| publisher= [[Prentice Hall]]| location= New Jersey| isbn= 978-0-13-066997-1}}</ref><ref>{{cite book| last= Chang| first= Raymond| title= Chemistry | url= https://archive.org/details/chemistry00chan_0| url-access= registration|edition=6th| date= 1998| publisher= [[McGraw Hill]]| location= New York| isbn= 978-0-07-115221-1}}</ref><ref>{{cite book| author= Zumdahl, Steven S.| title= Chemistry |edition=4th| date= 1997| publisher= Houghton Mifflin| location= Boston| isbn= 978-0-669-41794-4}}</ref> Molecules are distinguished from [[ion]]s by their lack of [[electrical charge]].

In [[quantum physics]], [[organic chemistry]], and [[biochemistry]], the distinction from ions is dropped and ''molecule'' is often used when referring to [[polyatomic ion]]s.

In the [[kinetic theory of gases]], the term ''molecule'' is often used for any gaseous [[particle]] regardless of its composition. This violates the definition that a molecule contain ''two or more'' atoms, since the [[noble gases]] are individual atoms.<ref>{{cite book| last= Chandra| first= Sulekh| title= Comprehensive Inorganic Chemistry| date= 2005| publisher= New Age Publishers| isbn= 978-81-224-1512-4}}</ref>

A molecule may be [[homonuclear]], that is, it consists of atoms of one [[chemical element]], as with two atoms in the [[oxygen]] molecule (O<sub>2</sub>); or it may be [[heteronuclear]], a [[chemical compound]] composed of more than one element, as with [[water (molecule)|water]] (two hydrogen atoms and one oxygen atom; H<sub>2</sub>O).

Atoms and complexes connected by [[non-covalent interactions]], such as [[hydrogen bond]]s or [[ionic bond]]s, are typically not considered single molecules.<ref>{{cite encyclopedia|title= Molecule|encyclopedia=[[Encyclopædia Britannica]]|date =22 January 2016|url=http://global.britannica.com/science/molecule|access-date=23 February 2016}}</ref>}}
{{term|term= '''[[Molecular physics]]'''}}{{defn|defn=Is the study of the physical properties of [[molecule]]s, the [[chemical bond]]s between [[atom]]s as well as the [[molecular dynamics]].  Its most important experimental techniques are the various types of [[spectroscopy]]; [[scattering]] is also used. The field is closely related to [[atomic physics]] and overlaps greatly with [[theoretical chemistry]], [[physical chemistry]] and [[chemical physics]].<ref>{{Cite web |url=https://www.chegg.com/homework-help/definitions/molecular-physics-204 |title=Molecular Physics  |access-date=2021-09-13 |archive-date=2019-11-16 |archive-url=https://web.archive.org/web/20191116190550/https://www.chegg.com/homework-help/definitions/molecular-physics-204 |url-status=dead }}</ref>}}
{{term|term= '''[[Moment of inertia]]'''}}{{defn|defn=The moment of inertia, otherwise known as the '''mass moment of inertia''', '''angular mass''', '''second moment of mass''', or most accurately, '''rotational inertia''', of a [[rigid body]] is a quantity that determines the [[torque]] needed for a desired [[angular acceleration]] about a rotational axis, akin to how [[mass]] determines the [[force]] needed for a desired [[acceleration]]. It depends on the body's mass distribution and the axis chosen, with larger moments requiring more torque to change the body's rate of rotation.}}
{{term|term= '''[[Multibody system]]'''}}{{defn|defn=Is the study of the dynamic behavior of interconnected rigid or flexible bodies, each of which may undergo large [[Translation (physics)|translational]] and [[rotational]] displacements.}}
{{term|term= '''[[Multidisciplinary design optimization]]'''}}{{defn|defn=(MDO), is a field of [[engineering]] that uses [[optimization (mathematics)|optimization]] methods to solve [[design]] problems incorporating a number of disciplines. It is also known as multidisciplinary system design optimization (MSDO).

MDO allows designers to incorporate all relevant disciplines simultaneously.  The optimum of the simultaneous problem is superior to the design found by optimizing each discipline sequentially, since it can exploit the interactions between the disciplines.  However, including all disciplines simultaneously significantly increases the [[computational complexity theory|complexity]] of the problem.}}
{{term|term= '''Mutual inductance'''}}{{defn|defn=Is the ratio between the [[electromotive force]] induced in one loop or coil by the rate of change of current in another loop or coil. Mutual inductance is given the symbol M.}}
{{term|term= '''[[Muon]]'''}}{{defn|defn=The muon, from the [[Greek alphabet|Greek]] letter [[mu (letter)|mu]] (μ) used to represent it) is an [[elementary particle]] similar to the [[electron]], with an [[electric charge]] of &minus;1&nbsp;''e'' and a [[spin-{{frac|1|2}}|spin of]] 1/2, but with a much greater mass. It is classified as a [[lepton]]. As with other leptons, the muon is not known to have any sub-structure – that is, it is not thought to be composed of any simpler particles.

The muon is an unstable [[subatomic particle]] with a [[mean lifetime]] of {{val|2.2|ul=μs}}, much longer than many other subatomic particles. As with the decay of the non-elementary [[neutron]] (with a lifetime around 15 minutes), muon decay is slow (by subatomic standards) because the decay is mediated only by the [[weak interaction]] (rather than the more powerful [[strong interaction]] or [[electromagnetic interaction]]), and because the mass difference between the muon and the set of its decay products is small, providing few kinetic [[degrees of freedom]] for decay. Muon decay almost always produces at least three particles, which must include an [[electron]] of the same charge as the muon and two types of [[neutrino]]s.}}

{{glossary end}}

== N ==
{{glossary}}

{{term|term='''[[Nanoengineering]]'''}}{{defn|defn=Is the practice of [[engineering]] on the [[Nanoscopic scale|nanoscale]]. It derives its name from the [[nanometre]], a unit of measurement equalling one billionth of a meter. Nanoengineering is largely a synonym for [[nanotechnology]], but emphasizes the engineering rather than the pure science aspects of the field.}} 
{{term|term='''[[Nanotechnology]]'''}}{{defn|defn=The technology of systems built with moving parts on the order of a nanometre in size.}} 
{{term|term='''[[Navier–Stokes equations]]'''}}{{defn|defn=In [[physics]], the Navier–Stokes equations are a set of [[partial differential equation]]s which describe the motion of [[viscous fluid]] substances, named after French engineer and physicist [[Claude-Louis Navier]] and Anglo-Irish physicist and mathematician [[Sir George Stokes, 1st Baronet|George Gabriel Stokes]].}}
{{term|term='''[[Neutrino]]'''}}{{defn|defn=A neutrino (denoted by the Greek letter {{math|[[Nu (letter)|ν]]}}) is a [[fermion]] (an [[elementary particle]] with [[spin-1/2|spin of {{sfrac|1|2}}]]) that interacts only via the [[weak interaction|weak subatomic force]] and [[gravity]].<ref>Close, Frank (2010). Neutrinos (softcover ed.). Oxford University Press. {{ISBN|978-0-199-69599-7}}.</ref><ref name="Jayawardhana"/> The neutrino is so named because it is [[electric charge|electrically]] neutral and because its [[rest mass]] is so small (''[[List of diminutives by language#Italian|-ino]]'') that it was long thought to be zero. The [[mass]] of the neutrino is much smaller than that of the other known elementary particles.<ref>Mertens, Susanne (2016). "Direct neutrino mass experiments". Journal of Physics: Conference Series. 718 (2): 022013. arXiv:1605.01579. Bibcode:2016JPhCS.718b2013M. doi:10.1088/1742-6596/718/2/022013. S2CID 56355240.</ref> The weak force has a very short range, the gravitational interaction is extremely weak, and neutrinos do not participate in the [[strong interaction]].<ref name="NYT-20200415">{{cite news |last=Overbye |first=Dennis |author-link=Dennis Overbye |title=Why The Big Bang Produced Something Rather Than Nothing - How did matter gain the edge over antimatter in the early universe? Maybe, just maybe, neutrinos. |url=https://www.nytimes.com/2020/04/15/science/physics-neutrino-antimatter-ichikawa-t2k.html |date=15 April 2020 |work=[[The New York Times]] |access-date=16 April 2020 }}</ref> Thus, neutrinos typically pass through normal matter unimpeded and undetected.<ref>{{cite book |title=Neutrinos |author=Close, Frank |year=2010 |publisher=[[Oxford University Press]] |edition=softcover |isbn=978-0-199-69599-7}}</ref><ref name="Jayawardhana">{{cite book |title=The Neutrino Hunters: The chase for the ghost particle and the secrets of the universe |author=Jayawardhana, Ray |year=2015 |publisher=[[Oneworld Publications]] |edition=softcover |isbn=978-1-780-74647-0}}</ref>}}
{{term|term='''[[Newtonian fluid]]'''}}{{defn|defn=Is a [[fluid]] in which the [[viscous stress tensor|viscous stresses]] arising from its [[Fluid dynamics|flow]], at every point, are linearly<ref>{{cite book |first=Ronald L. |last=Panton |title=Incompressible Flow |edition=Fourth |year=2013 |publisher=John Wiley & Sons |location=Hoboken |page=114 |isbn=978-1-118-01343-4 }}</ref> correlated to the local [[strain rate]]—the [[derivative (mathematics)|rate of change]] of its [[deformation (mechanics)|deformation]] over time.<ref>{{cite book |first= G. K. |last=Batchelor |author-link=George Batchelor |title= An Introduction to Fluid Dynamics |publisher= Cambridge Mathematical Library series, Cambridge University Press |year=2000 |orig-year= 1967 |url= https://books.google.com/books?id=Rla7OihRvUgC&q=An%20Introduction%20to%20Fluid%20Dynamics&pg=PP1 |isbn=978-0-521-66396-0}}</ref><ref name=Kundu>{{cite book |last1= Kundu |first1=P. |last2=Cohen |first2=I. |title= Fluid Mechanics |page= (page needed)}}</ref><ref name=Kirby>{{cite book |last= Kirby |first=B. J. |title= Micro- and Nanoscale Fluid Mechanics: Transport in Microfluidic Devices |url= http://www.kirbyresearch.com/textbook | year= 2010| publisher=Cambridge University Press |isbn=978-0-521-11903-0}}</ref> That is equivalent to saying those forces are proportional to the rates of change of the fluid's [[velocity|velocity vector]] as one moves away from the point in question in various directions. More precisely, a fluid is Newtonian only if the [[tensor]]s that describe the viscous stress and the strain rate are related by a constant [[viscosity|viscosity tensor]] that does not depend on the stress state and velocity of the flow. If the fluid is also [[isotropic]] (that is, its mechanical properties are the same along any direction), the viscosity tensor reduces to two real coefficients, describing the fluid's resistance to continuous [[Shearing (physics)|shear deformation]] and continuous [[compression (physical)|compression]] or expansion, respectively.}}
{{term|term='''[[Norton's theorem]]'''}}{{defn|defn=In direct-current [[circuit theory]], Norton's theorem (aka ''Mayer–Norton theorem'') is a simplification that can be applied to networks made of linear time-invariant resistances, voltage sources, and current sources. At a pair of terminals of the network, it can be replaced by a current source and a single resistor in parallel. For [[alternating current]] (AC) systems the theorem can be applied to [[Reactive power|reactive]] [[Electrical impedance|impedances]] as well as resistances.}}
{{term|term='''[[Nozzle]]'''}}{{defn|defn=Is a device designed to control the direction or characteristics of a [[fluid]] flow (especially to increase velocity) as it exits (or enters) an enclosed chamber or [[pipe (material)|pipe]]. A nozzle is often a pipe or tube of varying cross sectional area, and it can be used to direct or modify the flow of a fluid ([[liquid]] or [[gas]]). Nozzles are frequently used to control the rate of flow, speed, direction, mass, shape, and/or the pressure of the stream that emerges from them. In a nozzle, the velocity of fluid increases at the expense of its pressure energy.}}
{{term|term='''[[Nth root|''n''th root]]'''}}{{defn|defn=To put a number of function to the exponential power of 1/n.}} 
{{term|term='''[[Nuclear binding energy]]'''}}{{defn|defn=The difference between the total mass energy of a nucleus and the mass energy of the isolated nucleons.}}
{{term|term='''[[Nuclear engineering]]'''}}{{defn|defn=The profession that deals with nuclear power.}}
{{term|term='''[[Nuclear fusion]]'''}}{{defn|defn=Is a [[nuclear reaction|reaction]] in which two or more [[atomic nuclei]] are combined to form one or more different atomic nuclei and subatomic particles ([[neutrons]] or [[protons]]). The difference in mass between the reactants and products is manifested as either the release or the absorption of [[energy]]. This difference in mass arises due to the difference in [[Nuclear binding energy|atomic binding energy]] between the nuclei before and after the reaction. Fusion is the process that powers active or [[main sequence]] [[star]]s and other [[Absolute magnitude|high-magnitude]] stars, where large amounts of energy are [[Proton–proton chain reaction|released]].}}
{{term|term='''[[Nuclear physics]]'''}}{{defn|defn=The science that describes the components of atoms.}}
{{term|term='''[[Nuclear potential energy]]'''}}{{defn|defn=The energy that is given up in decay of an unstable nucleus.}}
{{term|term='''[[Nuclear power]]'''}}{{defn|defn=The use of energy derived from nuclear chain reactions for electricity production or ship propulsion.}}
{{glossary end}}

== O ==
{{glossary}}

{{term|term='''[[Ohm]]'''}}{{defn|defn=The SI unit of electrical resistance.}} 
{{term|term='''[[Ohm's law]]'''}}{{defn|defn=A law describing the relationship between resistance, current, and voltage.}} 
{{term|term='''[[Optics]]'''}}{{defn|defn=The study of light.}}
{{term|term='''[[Organic chemistry]]'''}}{{defn|defn=The study of carbon compounds.}}
{{term|term='''[[Osmosis]]'''}}{{defn|defn=The spontaneous movement of molecules or ions through a semi-permable membrane, tending to equalize concentration on both sides.}}
{{glossary end}}

== P ==
{{glossary}}

{{term|term='''[[Parallel circuit]]'''}}{{defn|defn=A circuit that begins and ends at the same node as another circuit.}} 
{{term|term='''[[Parity (mathematics)]]'''}}{{defn|defn=In [[mathematics]], parity is the property of an [[integer]] of whether it is even or odd. An integer's parity is even if it is [[divisible]] by two with no remainders left and its parity is odd if its remainder is 1.<ref name="rod">{{citation|title=Figuring Out Mathematics|last1=Vijaya|first1=A.V.|last2=Rodriguez|first2=Dora |publisher=Pearson Education India|isbn=9788131703571|pages=20–21|url=https://books.google.com/books?id=9ZN9LuHb0tQC&pg=PA20}}.</ref> For example, -4, 0, 82, and 178 are even because there is no [[remainder]] when dividing it by 2. By contrast, -3, 5, 7, 21 are odd numbers as they leave a remainder of 1 when divided by 2.}}
{{term|term='''[[Parity (physics)]]'''}}{{defn|defn=In [[quantum mechanics]], a parity transformation (also called parity inversion) is the flip in the sign of ''one'' [[Three-dimensional space|spatial]] [[coordinate]]. In three dimensions, it can also refer to the simultaneous flip in the sign of all three spatial coordinates (a [[point reflection]]):

:<math>\mathbf{P}: \begin{pmatrix}x\\y\\z\end{pmatrix} \mapsto \begin{pmatrix}-x\\-y\\-z\end{pmatrix}.</math>

It can also be thought of as a test for [[Chirality (physics)|chirality]] of a physical phenomenon, in that a parity inversion transforms a phenomenon into its mirror image. All fundamental interactions of [[elementary particle]]s, with the exception of the [[weak interaction]], are symmetric under parity. The weak interaction is chiral and thus provides a means for probing chirality in physics. In interactions that are symmetric under parity, such as electromagnetism in atomic and molecular physics, parity serves as a powerful controlling principle underlying quantum transitions.

A matrix representation of '''P''' (in any number of dimensions) has [[determinant]] equal to −1, and hence is distinct from a [[rotation]], which has a determinant equal to 1. In a two-dimensional plane, a simultaneous flip of all coordinates in sign is ''not'' a parity transformation; it is the same as a 180°-[[rotation]].

In [[quantum mechanics]], wave functions that are unchanged by a parity transformation are described as [[Even and odd functions|even]] functions, while those that change sign under a parity transformation are odd functions.fn=A hydrocarbon compound, solid at room temperature.}} 
{{term|term='''[[Paramagnetism]]'''}}{{defn|defn=Is a form of [[magnetism]] whereby some materials are weakly attracted by an externally applied [[magnetic field]], and form internal, [[Magnetization|induced magnetic field]]s in the direction of the applied magnetic field. In contrast with this behavior, [[diamagnetism|diamagnetic]] materials are repelled by magnetic fields and form induced magnetic fields in the direction opposite to that of the applied magnetic field.<ref>Miessler, G. L. and Tarr, D. A. (2010) ''Inorganic Chemistry'' 3rd ed., Pearson/Prentice Hall publisher, {{ISBN|0-13-035471-6}}.</ref> Paramagnetic materials include most [[chemical element]]s and some compounds;<ref>[https://global.britannica.com/science/paramagnetism britannica.com]</ref> they have a relative [[magnetic permeability]] slightly greater than 1 (i.e., a small positive [[magnetic susceptibility]]) and hence are attracted to magnetic fields. The [[magnetic moment]] induced by the applied field is linear in the field strength and rather weak. It typically requires a sensitive analytical balance to detect the effect and modern measurements on paramagnetic materials are often conducted with a [[SQUID]] [[magnetometer]].}}
{{term|term='''[[Particle accelerator]]'''}}{{defn|defn=Is a machine that uses [[electromagnetic field]]s to propel [[electric charge|charged]] [[particle]]s to very high speeds and energies, and to contain them in well-defined [[particle beam|beams]].<ref>{{Cite book 
 |last1=Livingston |first1=M. S. | author-link1 = Milton Stanley Livingston
 |last2=Blewett |first2=J.
 |year=1969 
 |title=Particle Accelerators
 |publisher=[[McGraw-Hill]]
 |location=New York
 |isbn=978-1-114-44384-6
}}</ref>}}
{{term|term='''[[Particle displacement]]'''}}{{defn|defn=Particle displacement or displacement amplitude is a [[measurement]] of [[distance]] of the movement of a [[sound particle]] from its [[mechanical equilibrium|equilibrium]] position in a medium as it transmits a sound wave.<ref>
{{cite book
 | title = Microsensors, MEMS, and Smart Devices John 2 | year = 2001
 | isbn = 978-0-471-86109-6
 | pages = 23–322
 | url = https://books.google.com/books?id=ht69jE9ypSwC&pg=PA321
 | last1 = Gardner
 | first1 = Julian W.
 | last2 = Varadan
 | first2 = Vijay K.
 | last3 = Awadelkarim
 | first3 = Osama O.
 | publisher = Wiley
 }}</ref> 
The [[International System of Units|SI unit]] of particle displacement is the [[metre]] (m). In most cases this is a [[longitudinal wave]] of pressure (such as [[sound]]), but it can also be a [[transverse wave]], such as the [[oscillation|vibration]] of a taut string. In the case of a [[sound wave]] travelling through [[air]], the particle displacement is evident in the [[oscillation]]s of air [[molecule]]s with, and against, the direction in which the sound wave is travelling.<ref>{{cite book
 | author= Arthur Schuster
 | title=An Introduction to the Theory of Optics
 | publisher=London: Edward Arnold
 | year=1904
 | url = https://archive.org/details/bub_gb_Zb4KAAAAIAAJ
 | quote= An Introduction to the Theory of Optics By Arthur Schuster.
 }}</ref>}}
{{term|term='''[[Particle physics]]'''}}{{defn|defn=Particle physics (also known as ''high energy physics'') is a branch of [[physics]] that studies the nature of the particles that constitute [[matter]] and [[radiation]]. Although the word ''[[particle]]'' can refer to various types of very small objects (e.g. [[protons]], gas particles, or even household dust), {{em|particle physics}} usually investigates the irreducibly smallest detectable particles and the [[fundamental interaction]]s necessary to explain their behaviour. In current understanding, these [[elementary particle]]s are excitations of the [[Field (physics)#Quantum fields|quantum fields]] that also govern their interactions. The currently dominant theory explaining these fundamental particles and fields, along with their dynamics, is called the [[Standard Model]]. Thus, modern particle physics generally investigates the Standard Model and its various possible extensions, e.g. to the newest "known" particle, the [[Higgs boson]], or even to the oldest known force field, [[gravity]].<ref>{{cite web|url=http://home.web.cern.ch/topics/higgs-boson|title=The Higgs Boson |date=26 May 2023 |publisher=CERN}}</ref><ref>{{cite web | url=https://www.nobelprize.org/nobel_prizes/physics/laureates/2013/advanced-physicsprize2013.pdf | title=The BEH-Mechanism, Interactions with Short Range Forces and Scalar Particles | date=8 October 2013}}</ref>}}
{{term|term='''[[Pascal's law]]'''}}{{defn|defn=Pascal's law (also ''Pascal's principle''<ref>{{cite web|url=http://www.britannica.com/EBchecked/topic/445445/Pascals-principle|title=Pascal's principle - Definition, Example, & Facts|website=britannica.com|access-date=9 May 2018|url-status=live|archive-url=https://web.archive.org/web/20150602231705/http://www.britannica.com/EBchecked/topic/445445/Pascals-principle|archive-date=2 June 2015}}</ref><ref>{{cite web|url=https://www.grc.nasa.gov/www/k-12/WindTunnel/Activities/Pascals_principle.html|title=Pascal's Principle and Hydraulics|website=www.grc.nasa.gov|access-date=9 May 2018|url-status=dead|archive-url=https://web.archive.org/web/20180405051915/https://www.grc.nasa.gov/www/k-12/WindTunnel/Activities/Pascals_principle.html|archive-date=5 April 2018}}</ref><ref>{{cite web|url=http://hyperphysics.phy-astr.gsu.edu/hbase/pasc.html|title=Pressure|website=hyperphysics.phy-astr.gsu.edu|access-date=9 May 2018|url-status=live|archive-url=https://web.archive.org/web/20171028014050/http://hyperphysics.phy-astr.gsu.edu/hbase/pasc.html|archive-date=28 October 2017}}</ref> or the ''principle of transmission of fluid-pressure'') is a principle in [[fluid mechanics]] that states that a pressure change occurring anywhere in a confined incompressible fluid is transmitted throughout the fluid such that the same change occurs everywhere.<ref>{{cite book
 | last = Bloomfield
 | first = Louis
 | title = How Things Work: The Physics of Everyday Life
 | url = https://archive.org/details/howthingsworkphy00bloo_760
 | url-access = limited
 | publisher = [[John Wiley & Sons]]
 | year = 2006
 | page = [https://archive.org/details/howthingsworkphy00bloo_760/page/n168 153]
 | isbn = 978-0-471-46886-8 | edition = Third
 }}</ref> The law was established by [[French people|French]] [[mathematician]] [[Blaise Pascal]]<ref name=acottLaw>{{Cite journal |author=Acott, Chris |title=The diving "Law-ers": A brief resume of their lives |journal=[[South Pacific Underwater Medicine Society Journal]] |volume=29 |issue=1 |year=1999 |issn=0813-1988 |oclc=16986801 |url=http://archive.rubicon-foundation.org/5990 |access-date=2011-06-14 |url-status=usurped |archive-url=https://web.archive.org/web/20110402073203/http://archive.rubicon-foundation.org/5990 |archive-date=2011-04-02 }}.</ref> in 1647–48.<ref>{{cite web |last1=O'Connor |first1=J.J. |last2=Robertson |first2=E.F. |author-link1=John J. O'Connor (mathematician) |author-link2=Edmund F. Robertson |title=Étienne Pascal |url=http://www-history.mcs.st-andrews.ac.uk/Biographies/Pascal_Etienne.html |date=August 2006 |publisher=[[University of St Andrews|University of St. Andrews, Scotland]] |access-date=5 February 2010 |url-status=live |archive-url=https://web.archive.org/web/20100419181846/http://www-history.mcs.st-andrews.ac.uk/Biographies/Pascal_Etienne.html |archive-date=19 April 2010 }}</ref>}}
{{term|term='''[[Pendulum]]'''}}{{defn|defn=Is a weight suspended from a [[wikt:pivot|pivot]] so that it can swing freely.<ref>{{cite encyclopedia
 | title = Pendulum
 | encyclopedia = Miriam Webster's Collegiate Encyclopedia
 | page = 1241
 | publisher = Miriam Webster
 | year = 2000
 | isbn = 978-0-87779-017-4
  }}</ref> When a pendulum is displaced sideways from its resting, [[Mechanical equilibrium|equilibrium position]], it is subject to a [[restoring force]] due to [[gravity]] that will accelerate it back toward the equilibrium position. When released, the restoring force acting on the pendulum's mass causes it to [[oscillate]] about the equilibrium position, swinging back and forth. The time for one complete cycle, a left swing and a right swing, is called the [[Frequency|period]]. The period depends on the length of the pendulum and also to a slight degree on the [[amplitude]], the width of the pendulum's swing.}}
{{term|term='''[[Petroleum engineering]]'''}}{{defn|defn=Is a field of engineering concerned with the activities related to the production of [[Hydrocarbons]], which can be either [[crude oil]] or [[natural gas]].<ref name="pet eng 2">{{Cite web|url=https://www.bls.gov/ooh/architecture-and-engineering/petroleum-engineers.htm#tab-2|title=Petroleum Engineers: Occupational Outlook Handbook: U.S. Bureau of Labor Statistics|website=www.bls.gov|access-date=2018-02-06}}</ref> Exploration and production are deemed to fall within the [[Upstream (oil industry)|''upstream'']] sector of the oil and gas industry. [[Hydrocarbon exploration|Exploration]], by [[earth science|earth scientists]], and petroleum engineering are the oil and gas industry's two main subsurface disciplines, which focus on maximizing economic recovery of hydrocarbons from subsurface reservoirs. [[Petroleum geology]] and [[geophysics]] focus on provision of a static description of the hydrocarbon reservoir rock, while petroleum engineering focuses on estimation of the recoverable volume of this resource using a detailed understanding of the physical behavior of oil, water and gas within porous rock at very high pressure.}}
{{term|term='''[[pH]]'''}}{{defn|defn=A logarithmic measure of the concentration of  hydrogen ions in an acid or base solution.}} 
{{term|term='''[[Phase (matter)]]'''}}{{defn|defn=In the [[outline of physical science|physical sciences]], a phase is a region of space (a [[thermodynamic system]]), throughout which all physical properties of a material are essentially uniform.<ref>{{cite book|last=Modell|first=Michael|author2=Robert C. Reid|title=Thermodynamics and Its Applications|publisher=Prentice-Hall|location=Englewood Cliffs, NJ|date=1974|isbn=978-0-13-914861-3|url-access=registration|url=https://archive.org/details/thermodynamicsit00mode}}</ref><ref name="Fermi2012">{{cite book|author=Enrico Fermi|title=Thermodynamics|date=25 April 2012|publisher=Courier Corporation|isbn=978-0-486-13485-7}}</ref>{{rp|86}}<ref name="Adkins1983">{{cite book|author=Clement John Adkins|title=Equilibrium Thermodynamics|date=14 July 1983|publisher=Cambridge University Press|isbn=978-0-521-27456-2}}</ref>{{rp|3}} Examples of physical properties include [[density]], [[refractive index|index of refraction]], [[magnetization]] and chemical composition. A simple description is that a phase is a region of material that is chemically uniform, physically distinct, and (often) mechanically separable. In a system consisting of ice and water in a glass jar, the ice cubes are one phase, the water is a second phase, and the humid air is a third phase over the ice and water. The glass of the jar is another separate phase. (See {{section link|state of matter|Glass}})}}
{{term|term='''[[Phase (waves)]]'''}}{{defn|defn=In [[physics]] and [[mathematics]], the phase of a [[periodic function]] <math>F</math> of some [[real number|real]] variable <math>t</math> (such as time) is an [[angle]]-like quantity representing the fraction of the cycle covered up to <math>t</math>.  It is denoted <math>\phi(t)</math> and expressed in such a [[scale (ratio)|scale]] that it varies by one full [[turn (geometry)|turn]] as the variable <math>t</math> goes through each [[Period (physics)|period]] (and <math>F(t)</math> goes through each complete cycle).  It may be [[Measure (mathematics)|measured]] in any [[angular unit]] such as [[degree (angle)|degrees]] or [[radians]], thus increasing by 360° or <math>2\pi</math> as the variable <math>t</math> completes a full period.<ref name=Ballou2005>{{cite book |last=Ballou |first=Glen |title=Handbook for sound engineers |url=https://books.google.com/books?id=y0d9VA0lkogC&pg=PA1499 |edition=3 |year=2005 |publisher=Focal Press, Gulf Professional Publishing |isbn=978-0-240-80758-4 |page=1499}}</ref>}}
{{term|term='''[[Phase diagram]]'''}}{{defn|defn=A phase diagram in [[physical chemistry]], [[engineering]], [[mineralogy]], and [[materials science]] is a type of [[chart]] used to show conditions (pressure, temperature, volume, etc.) at which thermodynamically distinct [[phase (matter)|phases]] (such as solid, liquid or gaseous states) occur and coexist at [[thermodynamic equilibrium|equilibrium]].}} 
{{term|term='''[[Phase rule]]'''}}{{defn|defn=In [[thermodynamics]], the phase rule is a general principle governing "pVT" systems (that is, systems whose [[Thermodynamic state|states]] are completely described by the variables [[pressure]] ({{mvar|p}}), [[volume]] ({{mvar|V}}) and [[temperature]] ({{mvar|T}})) in [[thermodynamic equilibrium]]. If {{mvar|F}} is the number of [[Degrees of freedom (physics and chemistry)|degrees of freedom]], {{mvar|C}} is the number of [[Component (thermodynamics)|components]] and {{mvar|P}} is the number of [[Phase (matter)|phases]], then<ref>{{Cite book|last=Smith|first=Joe Mauk|title=Introduction to chemical engineering thermodynamics|publisher=McGraw-Hill Education|year=2018|isbn=978-1-259-69652-7|location=United States of America|pages=422}}</ref><ref name="Atkins">{{cite book |last1=Atkins |first1=Peter |last2=Paula |first2=Julio De |last3=Keeler |first3=James |title=Atkins' Physical chemistry |date=2018 |publisher=Oxford University Press |isbn=9780198769866 |pages=123&ndash;125 |edition=Eleventh}}</ref> 
:<math>F = C - P + 2.</math>
It was derived by American physicist [[Josiah Willard Gibbs]] in his landmark paper titled ''[[On the Equilibrium of Heterogeneous Substances]]'', published in parts between 1875 and 1878.<ref>{{citation|first=J. W.|last=Gibbs|author-link=Josiah Willard Gibbs|title=Scientific Papers |location=Dover, New York|year=1961}}</ref>
The rule assumes the components do not [[Chemical reaction|react]] with each other.}}
{{term|term='''[[Photon]]'''}}{{defn|defn=Is a type of [[elementary particle]]. It is the [[quantum]] of the [[electromagnetic field]] including [[electromagnetic radiation]] such as [[light]] and [[radio wave]]s, and the [[force carrier]] for the [[electromagnetic force]]. Photons are [[Massless particle|massless]],{{efn|The photon's [[invariant mass]] (also called "rest mass" for massive particles) is believed to be exactly zero.  This is the notion of particle mass generally used by modern physicists.  The photon does have a nonzero [[relativistic mass]], depending on its energy, but this varies according to the [[frame of reference]].}} so they always move at the [[speed of light|speed of light in vacuum]], {{val|299792458|u=m/s}} (or about {{convert|299792458|m/s|mi/s|disp=out|sigfig=6}}). The photon belongs to the class of [[bosons]].}}
{{term|term='''[[Physical chemistry]]'''}}{{defn|defn=Is the study of [[macroscopic scale|macroscopic]], and particulate phenomena in [[chemistry|chemical]] systems in terms of the principles, practices, and concepts of [[physics]] such as [[Motion (physics)|motion]], [[energy]], [[force]], [[time]], [[thermodynamics]], [[quantum chemistry]], [[statistical mechanics]], [[analytical dynamics]] and [[chemical equilibrium]].}}
{{term|term='''[[Physical quantity]]'''}}{{defn|defn=A physical quantity is a property of a material or system that can be [[Quantification (science)|quantified]] by [[measurement]]. A physical quantity can be expressed as a ''value'', which is the algebraic multiplication of a ''numerical value'' and a [[Unit of measurement|''unit'']]. For example, the physical quantity [[mass]] can be quantified as ''n'' [[kilogram|kg]], where ''n'' is the numerical value and kg is the unit. A physical quantity possesses at least two characteristics in common. One is numerical magnitude and the other is the unit in which it is measured.}}
{{term|term='''[[Physics]]'''}}{{defn|defn=Is the [[natural science]] that studies [[matter]],{{efn|At the start of ''[[The Feynman Lectures on Physics]]'', [[Richard Feynman]] offers the [[Atomic theory|atomic hypothesis]] as the single most prolific scientific concept.<ref name="feynmanleightonsands1963-atomic">{{harvnb|Feynman|Leighton|Sands|1963|p=I-2}} "If, in some cataclysm, all [] scientific knowledge were to be destroyed [save] one sentence&nbsp;[...] what statement would contain the most information in the fewest words? I believe it is&nbsp;[...] that ''all things are made up of atoms&nbsp;– little particles that move around in perpetual motion, attracting each other when they are a little distance apart, but repelling upon being squeezed into one another''&nbsp;..."</ref> }} its [[Motion (physics)|motion]] and behavior through [[Spacetime|space and time]], and the related entities of [[energy]] and [[force]].<ref name="maxwell1878-physicalscience">{{harvnb|Maxwell|1878|p=9}} "Physical science is that department of knowledge which relates to the order of nature, or, in other words, to the regular succession of events."</ref> Physics is one of the most fundamental [[science|scientific]] disciplines, and its main goal is to understand how the [[universe]] behaves.{{efn|The term "universe" is defined as everything that physically exists: the entirety of space and time, all forms of matter, energy and momentum, and the physical laws and constants that govern them. However, the term "universe" may also be used in slightly different contextual senses, denoting concepts such as the [[cosmos]] or the [[World (philosophy)|philosophical world]].}}<ref name="youngfreedman2014p1">{{harvnb |Young|Freedman|2014|p=1}} "Physics is one of the most fundamental of the sciences. Scientists of all disciplines use the ideas of physics, including chemists who study the structure of molecules, paleontologists who try to reconstruct how dinosaurs walked, and climatologists who study how human activities affect the atmosphere and oceans. Physics is also the foundation of all engineering and technology. No engineer could design a flat-screen TV, an interplanetary spacecraft, or even a better mousetrap without first understanding the basic laws of physics. (...) You will come to see physics as a towering achievement of the human intellect in its quest to understand our world and ourselves."</ref><ref name="youngfreedman2014p2">{{harvnb |Young|Freedman|2014|p=2}} "Physics is an experimental science. Physicists observe the phenomena of nature and try to find patterns that relate these phenomena."</ref><ref name="holzner2003-physics">{{harvnb|Holzner|2006|p=7}} "Physics is the study of your world and the world and universe around you."</ref>}}
{{term|term='''[[Planck constant]]'''}}{{defn|defn=The Planck constant, or '''Planck's constant''', is a fundamental [[physical constant]] denoted <math>h</math>, and is of fundamental importance in [[quantum mechanics]]. A [[photon]]'s energy is equal to its frequency multiplied by the Planck constant.  Due to [[mass–energy equivalence]], the Planck constant also relates mass to frequency.

In [[metrology]] it is used, together with other constants, to define the [[kilogram]], an [[SI unit]].<ref>{{SIbrochure9th|page=131}}</ref> The SI units are defined in such a way that, when the Planck constant is expressed in SI units, it has the exact value {{nowrap|<math>h</math> {{=}} {{physconst|h|after=.}}}}<ref>{{cite web|url=https://www.bipm.org/utils/common/pdf/CGPM-2018/26th-CGPM-Resolutions.pdf|date=2018-11-16|work=BIPM|access-date=2018-11-20|language=en-GB|title=Resolutions of the 26th CGPM|archive-url=https://web.archive.org/web/20181119214326/https://www.bipm.org/utils/common/pdf/CGPM-2018/26th-CGPM-Resolutions.pdf|archive-date=2018-11-19|url-status=dead}}</ref>}}
{{term|term='''[[Plasma (physics)]]'''}}{{defn|defn=Is one of the [[State of matter#Four fundamental states|four fundamental states of matter]], first systematically studied by [[Irving Langmuir]] in the 1920s.<ref name=Itpp1995>{{cite book |last1=Goldston |first1=R.J. |last2=Rutherford |first2=P.H. |date=1995 |title=Introduction to Plasma Physics |page=1−2 |publisher=Taylor & Francis |isbn=978-0-7503-0183-1 |url=https://books.google.com/books?id=7kM7yEFUGnAC&q=chen+%22introduction+to+plasma+physics%22}}</ref><ref name=Itpd2012a>{{cite book |last1=Morozov |first1=A.I.|date=2012 |title=Introduction to Plasma Dynamics |page=17 |publisher=CRC Press| isbn=978-1-4398-8132-3 |url=https://books.google.com/books?id=DB0L6P3TwiYC&q=Introduction+to+Plasma+Dynamics+morozov}}</ref> It consists of a gas of [[ion]]s – atoms or molecules which have one or more orbital electrons stripped (or, rarely, an extra electron attached), and free [[electron]]s.}}
{{term|term='''[[Plasticity (physics)|Plasticity]]'''}}{{defn|defn=In [[physics]] and [[materials science]], plasticity, also known as '''plastic deformation''', is the ability of a [[solid]] [[material]] to undergo permanent [[Deformation (engineering)|deformation]], a non-reversible change of shape in response to applied forces.<ref name="Lubliner">{{cite book |first=J. |last=Lubliner |year=2008 |title=Plasticity theory |publisher=Dover |isbn=978-0-486-46290-5 }}</ref><ref>{{cite book |last=Bigoni |first=D. |title=Nonlinear Solid Mechanics: Bifurcation Theory and Material Instability |publisher=Cambridge University Press |year=2012 |isbn=978-1-107-02541-7 }}</ref>  For example, a solid piece of metal being bent or pounded into a new shape displays plasticity as permanent changes occur within the material itself. In engineering, the transition from [[Elasticity (physics)|elastic]] behavior to plastic behavior is known as [[Yield (engineering)|yielding]].}}
{{term|term='''[[Pneumatics]]'''}}{{defn|defn=The control of mechanical force and movement, generated by the application of compressed gas.}}
{{term|term='''[[Point estimation]]'''}}{{defn|defn=In [[statistics]], point estimation involves the use of [[statistical sample|sample]] [[data]] to calculate a single value (known as a '''point estimate''' since it identifies a [[Point (geometry)|point]] in some [[parameter space]]) which is to serve as a "best guess" or "best estimate" of an unknown population [[parameter]] (for example, the [[population mean]]). More formally, it is the application of a point [[estimator]] to the data to obtain a point estimate.

Point estimation can be contrasted with [[interval estimation]]: such interval estimates are typically either [[confidence interval]]s, in the case of [[frequentist inference]], or [[credible intervals]], in the case of [[Bayesian inference]]. More generally, a point estimator can be contrasted with a set estimator. Examples are given by [[Confidence region|confidence sets]] or [[Credible interval|credible sets.]] A point estimator can also be contrasted with a distribution estimator. Examples are given by [[confidence distribution]]s, [[Randomised decision rule|randomized estimators]], and [[Bayesian statistics|Bayesian posteriors]].}} 
{{term|term='''[[Polyphase system]]'''}}{{defn|defn=An electrical system that uses a set of alternating currents at different phases.}} 
{{term|term='''[[Electric power|Power (electric)]]'''}}{{defn|defn=Electric power is the rate, per unit time, at which [[electrical energy]] is transferred by an [[electric circuit]]. The [[SI]] unit of [[Power (physics)|power]] is the [[watt]], one [[joule]] per [[second]].

Electric power is usually produced by [[electric generator]]s, but can also be supplied by sources such as [[Battery (electricity)|electric batteries]].  It is usually supplied to businesses and homes (as domestic [[mains electricity]]) by the [[electric power industry]] through an [[electric power grid]].

Electric power can be delivered over long distances by [[electric power transmission|transmission lines]] and used for applications such as [[Electric motor|motion]], [[Electric light|light]] or [[Electric heat|heat]] with high [[Electrical efficiency|efficiency]].<ref name="smith-2001">
{{cite book | last = Smith | first = Clare | title = Environmental Physics | date = 2001 | publisher = [[Routledge]] | location = London | isbn = 0-415-20191-8}}</ref>}}
{{term|term='''[[Power (physics)]]'''}}{{defn|defn=In physics, power is the amount of [[energy]] transferred or converted per unit time. In the [[International System of Units]], the unit of power is the [[watt]], equal to one [[joule]] per second. In older works, power is sometimes called ''activity''.<ref name="Smithsonian Tables">{{cite book|title=Smithsonian Physical Tables|publisher=[[Smithsonian Institution]]|date=1921|editor-first1=Frederick E.|editor-last1=Fowle|edition=7th revised|location=Washington, D.C.|url=https://books.google.com/books?id=tCoJAQAAIAAJ&q=%22Power%20or%20Activity%20is%20the%20time%20rate%20of%20doing%20work%22|oclc=1142734534|archive-url=https://web.archive.org/web/20200423151426/https://www.google.com/books/edition/Smithsonian_Physical_Tables/tCoJAQAAIAAJ?hl=en&gbpv=1&bsq=%22Power%20or%20Activity%20is%20the%20time%20rate%20of%20doing%20work%22|archive-date=23 April 2020|url-status=live|quote='''Power or Activity''' is the time rate of doing work, or if {{math|''W''}} represents work and {{math|''P''}} power, {{math|''P'' {{=}} ''dw/dt''}}. (p. xxviii) ... ACTIVITY. Power or rate of doing work; unit, the watt. (p. 435)}}</ref><ref name="Heron Motors">{{cite journal|last1=Heron|first1=C. A.|date=1906|title=Electrical Calculations for Rallway Motors|url=https://books.google.com/books?id=b5A4AQAAMAAJ&dq=%22The+activity+of+a+motor+is+the+work+done+per+second%22+%22Where+the+joule+is+employed+as+the+unit+of+work,+the+international+unit+of+activity+is+the+joule-per-second,+or,+as+it+is+commonly+called,+the+watt.%22&pg=PA78|journal=Purdue Eng. Rev.|issue=2|pages=77–93|access-date=23 April 2020|archive-url=https://web.archive.org/web/20200423142933/https://www.google.com/books/edition/The_Purdue_Engineering_Review/b5A4AQAAMAAJ?hl=en&gbpv=1&dq=%22The+activity+of+a+motor+is+the+work+done+per+second%22+%22Where+the+joule+is+employed+as+the+unit+of+work,+the+international+unit+of+activity+is+the+joule-per-second,+or,+as+it+is+commonly+called,+the+watt.%22&pg=PA78&printsec=frontcover|archive-date=23 April 2020|url-status=live|quote=The activity of a motor is the work done per second, ... Where the joule is employed as the unit of work, the international unit of activity is the joule-per-second, or, as it is commonly called, the watt. (p. 78)}}</ref><ref name="Nature 1902">{{cite journal|date=1902|title=Societies and Academies|journal=Nature|volume=66|issue=1700|pages=118–120|doi=10.1038/066118b0|bibcode=1902Natur..66R.118.|quote=If the watt is assumed as unit of activity...|doi-access=free}}</ref> Power is a [[Scalar (physics)|scalar]] quantity.}} 
{{term|term='''[[Power factor]]'''}}{{defn|defn=In [[electrical engineering]], the power factor of an [[AC power]] system is defined as the [[ratio]] of the ''[[real power]]'' absorbed by the [[electrical load|load]] to the ''[[apparent power]]'' flowing in the circuit, and is a [[dimensionless number]] in the [[closed interval]] of −1 to 1. A power factor of less than one indicates the voltage and current are not in phase, reducing the average [[Product (mathematics)|product]] of the two. Real power is the instantaneous product of voltage and current and represents the capacity of the electricity for performing work. Apparent power is the product of [[Root mean square|RMS]] current and voltage. Due to energy stored in the load and returned to the source, or due to a non-linear load that distorts the wave shape of the current drawn from the source, the apparent power may be greater than the real power. A negative power factor occurs when the device (which is normally the load) generates power, which then flows back towards the source.}} 
{{term|term='''[[Pressure]]'''}}{{defn|defn=Pressure (symbol: ''p'' or ''P'') is the [[force]] applied perpendicular to the surface of an object per unit [[area]] over which that force is distributed.{{rp|445}}<ref>{{cite book |last1=Knight, PhD |first1=Randall D. |title=Physics for Scientists and Engineers: A Strategic Approach |date=2007 |publisher=Pearson Addison Wesley |location=San Francisco |isbn=978-0-321-51671-8 |pages=1183 |edition=2nd |url=https://books.google.com/books?id=32yzygAACAAJ&q=Physics+for+Scientists+and+Engineers:+A+Strategic+Approach |access-date=6 April 2020 |language=en-us |format=google books |chapter=Fluid Mechanics |quote={{small|''Pressure itself is not a Force, even though we sometimes talk "informally" about the "force exerted by the pressure. The correct statement is that the Fluid exerts a force on a surface. In addition, Pressure is a scalar, not a vector.'' }}}}</ref> [[Gauge pressure]] (also spelled ''gage'' pressure)<ref group=lower-alpha>The preferred spelling varies by country and even by industry. Further, both spellings are often used ''within'' a particular industry or country. Industries in British English-speaking countries typically use the "gauge" spelling.</ref> is the pressure relative to the ambient pressure.

Various [[#Units|units]] are used to express pressure. Some of these derive from a unit of force divided by a unit of area; the [[International System of Units|SI]] unit of pressure, the [[Pascal (unit)|pascal]] (Pa), for example, is one [[newton (unit)|newton]] per [[square metre]] (N/m<sup>2</sup>); similarly, the [[Pound (force)|pound-force]] per [[square inch]] ([[Pounds per square inch|psi]]) is the traditional unit of pressure in the [[imperial units|imperial]] and [[United States customary units|U.S. customary]] systems. Pressure may also be expressed in terms of [[standard atmospheric pressure]]; the [[atmosphere (unit)|atmosphere]] (atm) is equal to this pressure, and the [[torr]] is defined as {{frac|760}} of this. Manometric units such as the [[centimetre of water]], [[millimetre of mercury]], and [[inch of mercury]] are used to express pressures in terms of the height of [[Pressure measurement#Liquid column (manometer)|column of a particular fluid]] in a manometer.}} 
{{term|term='''[[Probability]]'''}}{{defn|defn=Is the branch of [[mathematics]] concerning numerical descriptions of how likely an [[Event (probability theory)|event]] is to occur, or how likely it is that a proposition is true.  The probability of an event is a number between 0 and 1, where, roughly speaking, 0 indicates impossibility of the event and 1 indicates certainty.{{NoteTag|Strictly speaking, a probability of 0 indicates that an event [[almost surely|''almost'' never]] takes place, whereas a probability of 1 indicates than an event [[almost surely|''almost'' certainly]] takes place. This is an important distinction when the [[sample space]] is infinite. For example, for the [[continuous uniform distribution]] on the [[real number|real]] interval [5, 10], there are an infinite number of possible outcomes, and the probability of any given outcome being observed — for instance, exactly 7 — is 0. This means that when we make an observation, it will ''almost surely not'' be exactly 7. However, it does '''not''' mean that exactly 7 is ''impossible''. Ultimately some specific outcome (with probability 0) will be observed, and one possibility for that specific outcome is exactly 7.}}<ref name="Stuart and Ord 2009">"Kendall's Advanced Theory of Statistics, Volume 1: Distribution Theory", Alan Stuart and Keith Ord, 6th Ed, (2009), {{ISBN|978-0-534-24312-8}}.</ref><ref name="Feller">William Feller, ''An Introduction to Probability Theory and Its Applications'', (Vol 1),  3rd Ed, (1968), Wiley, {{ISBN|0-471-25708-7}}.</ref> The higher the probability of an event, the more likely it is that the event will occur. A simple example is the tossing of a fair (unbiased) coin. Since the coin is fair, the two outcomes ("heads" and "tails") are both equally probable; the probability of "heads" equals the probability of "tails"; and since no other outcomes are possible, the probability of either "heads" or "tails" is 1/2 (which could also be written as 0.5 or 50%).}} 
{{term|term='''[[Probability distribution]]'''}}{{defn|defn=In [[probability theory]] and [[statistics]], a probability distribution is the mathematical [[Function (mathematics)|function]] that gives the probabilities of occurrence of different possible '''outcomes''' for an [[Experiment (probability theory)|experiment]].<ref>{{Cite book|title=The Cambridge dictionary of statistics|last=Everitt, Brian.|date=2006|publisher=Cambridge University Press|isbn=978-0-511-24688-3 |edition=3rd|location=Cambridge, UK|oclc=161828328}}</ref><ref>{{Cite book|title=Basic probability theory|last=Ash, Robert B.|date=2008|publisher=Dover Publications|isbn=978-0-486-46628-6|edition=Dover|location=Mineola, N.Y. |pages=66–69|oclc=190785258}}</ref> It is a mathematical description of a [[Randomness|random]] phenomenon in terms of its [[sample space]] and the [[Probability|probabilities]] of [[Event (probability theory)|events]] (subsets of the sample space).<ref name="Renn, J. 2010, pg 1-2">Renn, J., Damerow, P., and McLaughlin, P. Aristotle, Archimedes, Euclid, and the Origin of Mechanics: The Perspective of Historical Epistemology. Berlin: Max Planck Institute for the History of Science, 2010, pg 1-2.</ref>

For instance, if {{mvar|X}} is used to denote the outcome of a coin toss ("the experiment"), then the probability distribution of {{mvar|X}} would take the value 0.5 (1 in 2 or 1/2) for {{math|''X''&nbsp;{{=}} heads}}, and 0.5 for {{math|''X''&nbsp;{{=}} tails}} (assuming that the coin is fair). Examples of random phenomena include the weather condition in a future date, the height of a randomly selected person, the fraction of male students in a school, the results of a [[Survey methodology|survey]] to be conducted, etc.<ref name="ross">{{cite book|first=Sheldon M.|last=Ross|title=A first course in probability|publisher=Pearson|year=2010}}</ref>}} 
{{term|term='''[[Probability theory]]'''}}{{defn|defn=is the branch of [[mathematics]] concerned with [[probability]]. Although there are several different [[probability interpretations]], probability theory treats the concept in a rigorous mathematical manner by expressing it through a set of [[axioms of probability|axioms]]. Typically these axioms formalise probability in terms of a [[probability space]], which assigns a [[measure (mathematics)|measure]] taking values between 0 and 1, termed the [[probability measure]], to a set of outcomes called the [[sample space]]. Any specified subset of these outcomes is called an [[event (probability theory)|event]].
Central subjects in probability theory include discrete and continuous [[random variable]]s, [[probability distributions]], and [[stochastic process]]es, which provide mathematical abstractions of [[determinism|non-deterministic]] or uncertain processes or measured [[Quantity|quantities]] that may either be single occurrences or evolve over time in a random fashion.
Although it is not possible to perfectly predict random events, much can be said about their behavior. Two major results in probability theory describing such behaviour are the [[law of large numbers]] and the [[central limit theorem]].

As a mathematical foundation for [[statistics]], probability theory is essential to many human activities that involve quantitative analysis of data.<ref>[http://home.ubalt.edu/ntsbarsh/stat-data/Topics.htm Inferring From Data<!-- Bot generated title -->]</ref> Methods of probability theory also apply to descriptions of complex systems given only partial knowledge of their state, as in [[statistical mechanics]] or [[sequential estimation]]. A great discovery of twentieth-century [[physics]] was the probabilistic nature of physical phenomena at atomic scales, described in [[quantum mechanics]].<ref>{{cite web |title=Why is quantum mechanics based on probability theory? |work=[[Stack Exchange]] |date=July 1, 2014|url=https://physics.stackexchange.com/q/69718 }}</ref>{{Unreliable source?|date=February 2016}}}} 
{{term|term='''[[Pulley]]'''}}{{defn|defn=Is a [[wheel]] on an [[axle]] or [[shaft (mechanical engineering)|shaft]] that is designed to support movement and change of direction of a taut cable or belt, or transfer of power between the shaft and cable or belt. In the case of a pulley supported by a frame or shell that does not transfer power to a shaft, but is used to guide the cable or exert a force, the supporting shell is called a block, and the pulley may be called a sheave.

A pulley may have a [[Groove (machining)|groove]] or grooves between [[flange]]s around its [[circumference]] to locate the cable or belt. The drive element of a pulley system can be a [[rope]], [[Wire rope|cable]], [[belt (mechanical)|belt]], or [[chain]].}}
{{term|term='''[[Pump]]'''}}{{defn|defn=Is a device that moves fluids ([[liquid]]s or [[gas]]es), or sometimes [[Slurry|slurries]], by mechanical action, typically converted from electrical energy into hydraulic energy. Pumps can be classified into three major groups according to the method they use to move the fluid: ''direct lift'', ''displacement'', and ''gravity'' pumps.<ref>[http://www.fao.org/docrep/010/ah810e/AH810E05.htm#5.3.1 Pump classifications]. Fao.org. Retrieved on 2011-05-25.</ref>

Pumps operate by some mechanism (typically [[Reciprocating motion|reciprocating]] or [[Rotation|rotary]]), and consume [[energy]] to perform [[mechanical work]] moving the fluid. Pumps operate via many energy sources, including manual operation, [[electricity]], [[engines]], or [[wind power]], and come in many sizes, from microscopic for use in medical applications, to large industrial pumps.}}
{{glossary end}}{{Glossary of engineering: M - Z ToC}}

== Q ==
{{glossary}}

{{term|term='''[[Quantum electrodynamics]]'''}}{{defn|defn=In particle physics, quantum electrodynamics (QED) is the [[relativity theory|relativistic]] [[quantum field theory]] of [[electrodynamics]]. In essence, it describes how [[light]] and [[matter]] interact and is the first theory where full agreement between [[quantum mechanics]] and [[special relativity]] is achieved. QED mathematically describes all [[phenomenon|phenomena]] involving [[electric charge|electrically charged]] particles interacting by means of exchange of [[photon]]s and represents the [[quantum mechanics|quantum]] counterpart of [[classical electromagnetism]] giving a complete account of matter and light interaction.}}
{{term|term='''[[Quantum field theory]]'''}}{{defn|defn=In [[theoretical physics]], quantum field theory (QFT) is a theoretical framework that combines [[classical field theory]], [[special relativity]] and [[quantum mechanics]],<ref name="peskin">{{cite book |last1=Peskin |first1=M. |author-link=Michael Peskin |last2=Schroeder |first2=D.
 |year=1995
 |title=An Introduction to Quantum Field Theory
 |url=https://books.google.com/books?id=i35LALN0GosC
 |publisher=[[Westview Press]]
 |isbn=978-0-201-50397-5 }}</ref>{{rp|xi}} but ''not'' [[general relativity]]'s description of [[gravity]]. QFT is used in [[particle physics]] to construct [[physical model]]s of [[subatomic particle]]s and in [[condensed matter physics]] to construct models of [[quasiparticle]]s.}}
{{term|term='''[[Quantum mechanics]]'''}}{{defn|defn=Is a fundamental theory in [[physics]] that provides a description of the physical properties of [[nature]] at the scale of [[atom]]s and [[subatomic particle]]s.<ref name="Feynman">{{cite book
 | last1 = Feynman
 | first1 = Richard
 | last2 = Leighton
 | first2 = Robert
 | last3 = Sands
 | first3 = Matthew
 | title = The Feynman Lectures on Physics, Vol. 3
 | publisher = California Institute of Technology
 | date = 1964
 | url = https://feynmanlectures.caltech.edu/III_01.html
 | isbn = 978-0201500646
 | access-date = 2020-12-19
 }}</ref>{{rp|1.1}} It is the foundation of all quantum physics including [[quantum chemistry]], [[quantum field theory]], [[quantum technology]], and [[quantum information science]].}}

{{glossary end}}

== R ==
{{glossary}}

{{term|term='''[[Regelation]]'''}}{{defn|defn=The phenomena of melting under pressure, then freezing when the pressure is reduced.}} 
{{term|term='''[[Relative density]]'''}}{{defn|defn=Relative density, or specific gravity,<ref name=specificgravity1>{{cite book| last = Dana| first = Edward Salisbury
|title = A text-book of mineralogy: with an extended treatise on crystallography...
|publisher = John Wiley and Sons| date = 1922| location = New York, London(Chapman Hall)
|pages = 195–200, 316
|url = https://books.google.com/books?id=rCwaAAAAYAAJ&pg=PA156}}</ref><ref name=specificgravity2>{{cite book
|last = Schetz| first = Joseph A.|author2=Allen E. Fuhs
 |title = Fundamentals of fluid mechanics| publisher =Wiley, John & Sons, Incorporated
|date =1999-02-05|pages = 111, 142, 144, 147, 109, 155, 157, 160, 175
|url =https://books.google.com/books?id=YCSSolzuu9IC&pg=PP1|isbn =0-471-34856-2}}</ref> is the [[ratio]] of the [[density]] (mass of a unit volume) of a substance to the density of a given reference material. Specific gravity for liquids is nearly always measured with respect to [[water (molecule)|water]] at its densest (at {{cvt|4|°C|°F|1|disp=or}}); for gases, the reference is air at [[room temperature]] ({{cvt|20|°C|°F|disp=or}}). The term "relative density" is often preferred in scientific usage.}} 
{{term|term='''[[Relative velocity]]'''}}{{defn|defn=The ''relative velocity'' <math>\vec{v}_{B\mid A}</math> (also <math>\vec{v}_{BA}</math> or <math>\vec{v}_{B \operatorname{rel} A}</math>) is the velocity of an object or observer '''B''' in the rest frame of another object or observer '''A'''.}}
{{term|term='''[[Reliability engineering]]'''}}{{defn|defn=Is a sub-discipline of [[systems engineering]] that emphasizes the ability of equipment to function without failure. Reliability describes the ability of a system or component to function under stated conditions for a specified period of time.<ref>Institute of Electrical and Electronics Engineers (1990) IEEE Standard Computer Dictionary: A Compilation of IEEE Standard Computer Glossaries. New York, NY {{ISBN|1-55937-079-3}}</ref> Reliability is closely related to [[availability]], which is typically described as the ability of a component or system to function at a specified moment or interval of time.}}
{{term|term='''[[Electrical resistivity and conductivity|Resistivity]]'''}}{{defn|defn=Electrical resistivity (also called specific electrical resistance or volume resistivity) and its inverse, electrical conductivity, is a fundamental property of  a material that quantifies how strongly it resists or conducts [[electric current]]. A low resistivity indicates a material that readily allows electric current. Resistivity is commonly represented by the [[Greek alphabet|Greek letter]] ''ρ''&nbsp;([[Rho (letter)|rho]]). The [[SI]] unit of electrical resistivity is the [[ohm]]-[[meter]] (Ω⋅m).<ref>{{cite book | last = Lowrie | first = William |  title = Fundamentals of Geophysics | url = https://books.google.com/books?id=h2-NjUg4RtEC&pg=PA254 | publisher = Cambridge University Press | isbn = 978-05-2185-902-8 | pages = 254–55 | date = 2007 | access-date = March 24, 2019 }}</ref><ref>{{cite book | first = Narinder | last = Kumar | title = Comprehensive Physics for Class XII | url = https://books.google.com/books?id=IryMtwHHngIC&pg=PA282 | date = 2003 | publisher = Laxmi Publications | location = New Delhi | isbn = 978-81-7008-592-8 | pages = 280–84 | access-date = March 24, 2019 }}</ref><ref>{{cite book | first = Eric | last = Bogatin | title = Signal Integrity: Simplified | url = https://books.google.com/books?id=_IiONSphoB4C&q=Signal%20integrity&pg=PA114 | year = 2004 | publisher = Prentice Hall Professional | isbn = 978-0-13-066946-9 | page = 114 | access-date = March 24, 2019 }}</ref> For example, if a {{nowrap|1 m × 1 m × 1 m}} solid cube of material has sheet contacts on two opposite faces, and the resistance between these contacts is 1&nbsp;Ω, then the resistivity of the material is 1&nbsp;Ω⋅m.}}
{{term|term='''[[Resistor]]'''}}{{defn|defn=Is a [[passivity (engineering)|passive]] [[terminal (electronics)|two-terminal]] [[electronic component|electrical component]] that implements [[electrical resistance]] as a circuit element. In electronic circuits, resistors are used to reduce current flow, adjust signal levels, to [[Voltage divider|divide voltages]], [[Biasing|bias]] active elements, and terminate [[transmission line]]s, among other uses. High-power resistors that can dissipate many [[watt]]s of electrical power as heat, may be used as part of motor controls, in power distribution systems, or as test loads for [[electric generator|generators]].
Fixed resistors have resistances that only change slightly with temperature, time or operating voltage. Variable resistors can be used to adjust circuit elements (such as a volume control or a lamp dimmer), or as sensing devices for heat, light, humidity, force, or chemical activity.}}
{{term|term='''[[Reynolds number]]'''}}{{defn|defn=The Reynolds number ({{math|Re}}) helps predict flow patterns in different fluid flow situations. At low Reynolds numbers, flows tend to be dominated by laminar (sheet-like) flow, while at high Reynolds numbers flows tend to be [[turbulent]]. The turbulence results from differences in the fluid's speed and direction, which may sometimes intersect or even move counter to the overall direction of the flow ([[Eddy (fluid dynamics)|eddy currents]]). These eddy currents begin to churn the flow, using up energy in the process, which for liquids increases the chances of [[cavitation]]. Reynolds numbers are an important [[dimensionless quantity]] in [[fluid mechanics]].}}
{{term|term='''[[Rheology]]'''}}{{defn|defn=Is the study of the flow of matter, primarily in a liquid or gas state, but also as "soft solids" or solids under conditions in which they respond with plastic flow rather than deforming elastically in response to an applied force. Rheology is a branch of physics, and it is the science that deals with the deformation and flow of materials, both solids and liquids.<ref name=Schowalter>W. R. Schowalter (1978) Mechanics of Non-Newtonian Fluids Pergamon {{ISBN|0-08-021778-8}}</ref>}}
{{term|term='''[[Rigid body]]'''}}{{defn|defn=In [[physics]], a rigid body (also known as a ''rigid object'' <ref>{{cite book|title=Introduction to Statics and Dynamics|author=Andy Ruina and Rudra Pratap|publisher=Oxford University Press|year=2015}} (link: [http://ruina.tam.cornell.edu/Book/])</ref>) is a solid [[Physical body|body]] in which [[deformation (engineering)|deformation]] is zero or so small it can be neglected. The [[distance]] between any two given [[Point (geometry)|point]]s on a rigid body remains constant in time regardless of external [[force]]s or [[Moment (physics)|moments]] exerted on it. A rigid body is usually considered as a [[continuum mechanics|continuous distribution]] of [[mass]]. In the study of [[special relativity]], a perfectly rigid body does not exist; and objects can only be assumed to be rigid if they are not moving near the [[speed of light]]. In [[quantum mechanics]], a rigid body is usually thought of as a collection of [[point particle|point masses]]. For instance, [[molecules]] (consisting of the point masses: electrons and nuclei) are often seen as rigid bodies (see [[Rotational spectroscopy#Classification of molecules based on rotational behavior|classification of molecules as rigid rotors]]).}}
{{term|term='''[[Robonaut]]'''}}{{defn|defn=A development project conducted by NASA to create humanoid robots capable of using space tools and working in similar environments to suited astronauts.}}
{{term|term='''[[Robot-assisted surgery]]'''}}{{defn|defn='''Robotic surgery''' are types of [[surgery|surgical procedures]] that are done using [[robot]]ic systems. Robotically-assisted surgery was developed to try to overcome the limitations of pre-existing [[minimally-invasive procedures|minimally-invasive surgical procedures]] and to enhance the capabilities of surgeons performing open surgery.

In the case of robotically-assisted minimally-invasive surgery, instead of directly moving the instruments, the surgeon uses one of two methods to administer the instruments. These include using a direct [[Remote manipulator|telemanipulator]] or through computer control. A telemanipulator is a remote manipulator that allows the surgeon to perform the normal movements associated with the surgery. The [[robotic arm]]s carry out those movements using [[robot end effector|end-effector]]s and [[manipulator (device)|manipulators]] to perform the actual surgery. In computer-controlled systems, the surgeon uses a computer to control the robotic arms and its end-effectors, though these systems can also still use telemanipulators for their input. One advantage of using the computerized method is that the surgeon does not have to be present, leading to the possibility for [[remote surgery]].}}
{{term|term='''[[Robotics]]'''}}{{defn|defn=Is an [[interdisciplinarity|interdisciplinary]] field that integrates [[computer science]] and [[engineering]].<ref>{{cite web|last=|first=|date=|title=German National Library|url=https://portal.dnb.de/opac.htm?method=simpleSearch&cqlMode=true&query=nid%3D4261462-4|access-date=|website=International classification system of the [[German National Library]] (GND)}}</ref> Robotics involves design, construction, operation, and use of [[robot]]s. The goal of robotics is to design machines that can help and assist humans. Robotics integrates fields of [[mechanical engineering]], [[electrical engineering]], [[Information engineering (field)|information engineering]], [[mechatronics]], [[electronics]], [[bioengineering]], [[computer engineering]], [[control engineering]], [[software engineering]], among others.}}
{{term|term='''[[Root mean square]]'''}}{{defn|defn=In [[mathematics]] and its applications, the root mean square (RMS or rms) is defined as the [[square root]] of the [[mean square]] (the [[arithmetic mean]] of the [[square (algebra)|squares]] of a [[Set (mathematics)|set]] of numbers).<ref name=dicphys>{{cite book
|title=A Dictionary of Physics (6 ed.)
|chapter=Root-mean-square value
|publisher=Oxford University Press
|year=2009
|isbn=9780199233991
|url=https://www.oxfordreference.com/view/10.1093/acref/9780199233991.001.0001/acref-9780199233991-e-2676
}}</ref>
The RMS is also known as the ''quadratic mean''<ref>{{cite book |last1=Thompson |first1=Sylvanus P. |title=Calculus Made Easy |date=1965 |publisher=[[Macmillan International Higher Education]] |isbn=9781349004874 |page=185 |url=https://books.google.com/books?id=6VJdDwAAQBAJ&pg=PA185 |access-date=5 July 2020 }}{{Dead link|date=May 2023 |bot=InternetArchiveBot |fix-attempted=yes }}</ref><ref>{{cite book |last1=Jones |first1=Alan R. |title=Probability, Statistics and Other Frightening Stuff |date=2018 |publisher=Routledge |isbn=9781351661386 |page=48 |url=https://books.google.com/books?id=OvtsDwAAQBAJ&pg=PA48 |access-date=5 July 2020}}</ref> and is a particular case of the [[generalized mean#Quadratic|generalized mean]] with exponent&nbsp;2. RMS can also be defined for a continuously varying [[function (mathematics)|function]] in terms of an [[integral]] of the squares of the instantaneous values during a cycle. For [[alternating current|alternating electric current]], RMS is equal to the value of the constant [[direct current]] that would produce the same power dissipation in a [[Resistor|resistive load]].<ref name=dicphys/> In [[estimation theory]], the [[root-mean-square deviation]] of an estimator is a measure of the imperfection of the fit of the estimator to the data.}}
{{term|term='''[[Root-mean-square speed]]'''}}{{defn|defn=In the [[physics]] of [[gas]] molecules, the root-mean-square speed is defined as the square root of the average squared-speed. The RMS speed of an ideal gas is [[Maxwell–Boltzmann distribution#Distribution for the velocity vector|calculated]] using the following equation:
:<math>v_\text{RMS} = \sqrt{3RT \over M}</math>

where ''R'' represents the [[gas constant]], 8.314&nbsp;J/(mol·K), ''T'' is the temperature of the gas in [[kelvin]]s, and ''M'' is the [[molar mass]] of the gas in kilograms per mole. In physics, speed is defined as the scalar magnitude of velocity. For a stationary gas, the average speed of its molecules can be in the order of thousands of km/h, even though the average velocity of its molecules is zero.}}
{{term|term='''[[Rotational energy]]'''}}{{defn|defn=Rotational energy or ''angular kinetic energy'' is [[kinetic energy]] due to the [[rotation around a fixed axis|rotation]] of an object and is part of its [[Kinetic energy#Rotation in systems|total kinetic energy]]. Looking at rotational energy separately around an object's [[axis of rotation]], the following dependence on the object's [[moment of inertia]] is observed:

:<math>E_\mathrm{rotational} = \frac{1}{2} I \omega^2 </math>
where
: <math> \omega \ </math> is the [[angular velocity]]
: <math> I \ </math> is the [[moment of inertia]] around the axis of rotation
: <math> E \ </math> is the [[kinetic energy]]}}
{{term|term='''[[Rotational speed]]'''}}{{defn|defn=Rotational speed (or ''speed of revolution'') of an object rotating around an axis is the number of [[Turn (geometry)|turns]] of the object divided by time, specified as [[revolutions per minute]] (rpm), [[cycles per second]] (cps), radians per second (rad/s), etc.<ref>{{Cite book
|last1=Atkins
|first1=Tony
|last2=Escudier
|first2=Marcel
|title=A Dictionary of Mechanical Engineering
|year=2013
|url=http://www.oxfordreference.com/view/10.1093/acref/9780199587438.001.0001/acref-9780199587438-e-5953?rskey=EBYJmx&result=1
|publisher=Oxford University Press
|isbn=9780199587438
}}</ref>

The symbol for rotational speed is <math>\omega_\text{cyc}</math>{{Citation needed|date=February 2015|reason=sub "cyc"?}}(the [[Greek alphabet|Greek]] lowercase letter "omega").

[[Speed#Tangential speed|Tangential speed]] ''v'', rotational speed <math>\omega_\text{cyc}</math>, and [[Polar coordinate system|radial distan]]ce ''r'', are related by the following equation:<ref>{{Cite web|url=http://hyperphysics.phy-astr.gsu.edu/hbase/rotq.html|title = Rotational Quantities}}</ref>

:<math>v = 2\pi r\omega_\text{cyc}</math>

:<math>v = r\omega_\text{rad}</math>

An algebraic rearrangement of this equation allows us to solve for rotational speed:

:<math>\omega_\text{cyc} = v/2\pi r</math>

:<math>\omega_\text{rad} = v/r</math>

Thus, the tangential speed will be directly proportional to ''r'' when all parts of a system simultaneously have the same ω, as for a wheel, disk, or rigid wand. The direct proportionality of ''v'' to ''r'' is not valid for the [[planet]]s, because the planets have different rotational speeds (ω).

Rotational speed can measure, for example, how fast a motor is running. Rotational speed and [[angular speed]] are sometimes used as synonyms, but typically they are measured with a different unit. Angular speed, however, tells the change in [[angle]] per time unit, which is measured in [[radian per second|radians per second]] in the SI system. Since there are 2π radians per cycle, or 360 degrees per cycle, we can convert angular speed to rotational speed by

:<math>\omega_\text{cyc} = \omega_\text{rad}/2\pi\,</math>
and
:<math>\omega_\text{cyc} = \omega_\text{deg}/360\,</math>

where
* <math>\omega_\text{cyc}\,</math> is rotational speed in cycles per second
* <math>\omega_\text{rad}\,</math> is angular speed in radians per second
* <math>\omega_\text{deg}\,</math> is angular speed in degrees per second

For example, a [[stepper motor]] might turn exactly one complete revolution each second.
Its angular speed is 360 [[degree (angle)|degrees]] per second (360°/s), or 2π [[radian]]s per second (2π rad/s), while the rotational speed is 60 rpm.

Rotational speed is not to be confused with [[Speed#Tangential speed|tangential speed]], despite some relation between the two concepts. Imagine a rotating merry-go-round. No matter how close or far you stand from the axis of rotation, your rotational speed will remain constant. However, your tangential speed does not remain constant. If you stand two meters from the axis of rotation, your tangential speed will be double the amount if you were standing only one meter from the axis of rotation.}}
{{glossary end}}{{Glossary of engineering: M - Z ToC}}

== S ==
{{glossary}}

{{term|term='''Safe failure fraction (SFF)'''}}{{defn|defn=A term used in [[functional safety]] for the proportion of failures that are either non-[[hazard]]ous or detected automatically. The opposite of SFF is the proportion of undetected, hazardous failures.<ref>{{cite web |title=Safe Failure Fraction |url=https://www.sciencedirect.com/topics/engineering/safe-failure-fraction |website=[[ScienceDirect]] |access-date=21 September 2020}}</ref>}}
{{term|term='''[[Safety data sheet]]'''}}{{defn|defn=A safety data sheet (SDS),<ref>{{cite web|url=http://www.unece.org/trans/danger/publi/ghs/ghs_rev04/04files_e.htmlUnited|title=Transport - Transport - UNECE|website=Unece.org|access-date=22 December 2017}}</ref> material safety data sheet (MSDS),  or product safety data sheet (PSDS) are documents that list information relating to [[occupational safety and health]] for the use of various substances and products. SDSs are a widely used system for cataloguing information on [[chemical]]s, [[chemical compound]]s, and chemical [[mixture]]s. SDS information may include instructions for the safe use and potential [[worker safety and health|hazards]] associated with a particular material or product, along with spill-handling procedures. The older MSDS formats could vary from source to source within a country depending on national requirements; however, the newer SDS format is internationally standardized.}}
{{term|term='''[[Sanitary engineering]]'''}}{{defn|defn=Sanitary engineering, also known as public health engineering or wastewater engineering, is the application of engineering methods to improve [[sanitation]] of human communities, primarily by providing the removal and disposal of human waste, and in addition to the supply of safe [[potable water]].}}
{{term|term='''[[Saturated compound]]'''}}{{defn|defn=In [[chemistry]], a saturated compound is a [[chemical compound]] (or ion) that resists the addition reactions, such as [[hydrogenation]], [[oxidative addition]], and binding of a [[Lewis base]]. The term is used in many contexts and for many classes of chemical compounds. Overall, saturated compounds are less reactive than unsaturated compounds. Saturation is derived from the Latin word ''saturare'', meaning 'to fill')<ref>''[[Mosby's Medical, Nursing & Allied Health Dictionary]]'', Fourth Edition, Mosby-Year Book Inc., 1994, p. 1394</ref>}}
{{term|term='''[[Scalar (mathematics)]]'''}}{{defn|defn=.}}
{{term|term='''[[Scalar (physics)]]'''}}{{defn|defn=.}}
{{term|term='''[[Scalar multiplication]]'''}}{{defn|defn=In [[mathematics]], scalar multiplication is one of the basic operations defining a [[vector space]] in [[linear algebra]]<ref>{{cite book | last=Lay | first=David C. | title=Linear Algebra and Its Applications | url=https://archive.org/details/studyguidetoline0000layd | url-access=registration | publisher=[[Addison–Wesley]] | year=2006 | edition = 3rd | isbn=0-321-28713-4}}</ref><ref>{{cite book | last=Strang | first=Gilbert | author-link=Gilbert Strang | title=Linear Algebra and Its Applications | publisher=[[Brooks Cole]] | year=2006 | edition = 4th | isbn=0-03-010567-6}}</ref><ref>{{cite book | last = Axler | first = Sheldon | title = Linear Algebra Done Right | publisher = [[Springer Science+Business Media|Springer]] | year = 2002 | edition = 2nd | isbn = 0-387-98258-2}}</ref> (or more generally, a [[module (mathematics)|module]] in [[abstract algebra]]<ref>{{cite book | last1=Dummit | first1=David S. | last2=Foote | first2=Richard M. | title=Abstract Algebra | publisher=[[John Wiley & Sons]] | year=2004 | edition=3rd | isbn=0-471-43334-9}}</ref><ref>{{cite book | last=Lang | first=Serge | author-link=Serge Lang | title=Algebra | publisher=[[Springer Science+Business Media|Springer]] | series=[[Graduate Texts in Mathematics]] | year=2002 | isbn=0-387-95385-X}}</ref>). In common geometrical contexts, scalar multiplication of a [[real number|real]] [[Euclidean vector]] by a positive real number multiplies the magnitude of the vector—without changing its direction. The term "[[Scalar (mathematics)|scalar]]" itself derives from this usage: a scalar is that which [[uniform scaling|scales]] vectors. Scalar multiplication is the multiplication of a vector by a scalar (where the product is a vector), and is to be distinguished from [[inner product]] of two vectors (where the product is a scalar).}}
{{term|term='''[[Screw (simple machine)|Screw]]'''}}{{defn|defn=A screw is a mechanism that converts [[rotation]]al motion to [[linear motion]], and a [[torque]] (rotational force) to a linear [[force]].<ref name="Young" >{{cite web
  | last = Young
  | first = James F.
  | title = Basic Mechanics
  | work = ELEC 201:Introduction to Engineering Design
  | publisher = Electrical and Computer Engineering Dept., Rice Univ.
  | year = 2000
  | url = http://www.clear.rice.edu/elec201/Book/basic_mech.html
  | access-date = 2011-03-29}}</ref> It is one of the six classical [[simple machine]]s. The most common form consists of a cylindrical shaft with [[Helix|helical]] grooves or ridges called ''[[Screw thread|threads]]'' around the outside.<ref>{{cite book
  | last = Morris
  | first = William, Ed.
  | title = The American Heritage Dictionary, New College Edition
  | publisher = Houghton Mifflin
  | year = 1979
  | location = USA
  | pages = [https://archive.org/details/americanheritag00morr/page/1167 1167]
  | url = https://archive.org/details/americanheritag00morr/page/1167
  | isbn = 0-395-20360-0
  }}</ref><ref>{{cite web
  | title = Screw
  | work = How Stuff Works website
  | publisher = Discovery Communications
  | year = 2011
  | url = http://science.howstuffworks.com/screw-info.htm
  | access-date = 2011-03-29}}</ref> The screw passes through a hole in another object or medium, with threads on the inside of the hole that mesh with the screw's threads. When the shaft of the screw is rotated relative to the stationary threads, the screw moves along its axis relative to the medium surrounding it; for example rotating a [[wood screw]] forces it into wood. In screw mechanisms, either the screw shaft can rotate through a threaded hole in a stationary object, or a threaded collar such as a [[nut (hardware)|nut]] can rotate around a stationary screw shaft.<ref name="Collins">{{cite book   
  | last = Collins
  | first = Jack A. 
  |author2=Henry R. Busby |author3=George H. Staab
   | title = Mechanical Design of Machine Elements and Machines, 2nd Ed
  | publisher = John Wiley and Sons
  | year = 2009
  | location = USA
  | pages = 462–463
  | url = https://books.google.com/books?id=909-5C4eyUkC&q=screw+machine+lead+pitch+advantage&pg=PA464
  | isbn = 978-0-470-41303-6}}</ref><ref name="Bhandari">{{cite book   
  | last = Bhandari
  | first = V. B.
  | title = Design of machine elements
  | publisher = Tata McGraw-Hill
  | year = 2007
  | location = New Delhi
  | pages = 202–206
  | url = https://books.google.com/books?id=d-eNe-VRc1oC&q=%22simple+machine%22+scr&pg=PP12
  | isbn = 978-0-07-061141-2}}</ref>  Geometrically, a screw can be viewed as a narrow [[inclined plane]] wrapped around a [[cylinder (geometry)|cylinder]].<ref name="Young" />}}
{{term|term='''[[Series circuit]]'''}}{{defn|defn=An electrical circuit in which the same current passes through each component, with only one path.}}
{{term|term='''[[Servo motor|Servo]]'''}}{{defn|defn=A motor that moves to and maintains a set position under command, rather than continuously moving.}} 
{{term|term='''[[Servomechanism]]'''}}{{defn|defn=An automatic device that uses error-sensing negative feedback to correct the performance of a mechanism.}} 
{{term|term='''[[Shadow matter]]'''}}{{defn|defn=In [[physics]], mirror matter, also called shadow matter or Alice matter, is a hypothetical counterpart to ordinary matter.<ref name="urlSigns of dark matter may point to mirror matter candidate">{{cite web |url=https://phys.org/news/2010-04-dark-mirror-candidate.html |title=Signs of dark matter may point to mirror matter candidate }}</ref>}}
{{term|term='''[[Shear flow]]'''}}{{defn|defn=The term shear flow is used in [[solid mechanics]] as well as in [[fluid dynamics]].  The expression ''shear flow'' is used to indicate:
* a [[shear stress]] over a distance in a thin-walled structure (in solid mechanics);<ref name=HOSW4-9>Higdon, Ohlsen, Stiles and Weese (1960), ''Mechanics of Materials'', article 4-9 (2nd edition), John Wiley & Sons, Inc., New York. Library of Congress CCN 66-25222</ref>
* the flow ''induced'' by a force (in a fluid).}}
{{term|term='''[[Shear strength]]'''}}{{defn|defn=Is the strength of a material or component against the type of [[Yield (engineering)|yield]] or [[structural failure]] when the material or component fails in [[Shearing (physics)|shear]]. A shear load is a [[force]] that tends to produce a sliding failure on a material along a plane that is parallel to the direction of the force. When a paper is cut with scissors, the paper fails in shear.

In [[structural engineering|structural]] and  [[mechanical engineering]], the shear strength of a component is important for designing the dimensions and materials to be used for the manufacture or construction of the component (e.g. [[beam (structure)|beams]], [[Plate (structures)|plates]], or [[Screw|bolts]]). In a [[reinforced concrete]] beam, the main purpose of [[Rebar#Stirrups|reinforcing bar (rebar) stirrups]] is to increase the shear strength.}}
{{term|term='''[[Shear stress]]'''}}{{defn|defn=Shear stress, often denoted by '''{{mvar|τ}}''' ([[Greek alphabet|Greek]]: [[tau]]), is the component of [[stress (physics)|stress]] coplanar with a material cross section. It arises from the [[shear force]], the component of [[force]] vector [[parallel (geometry)|parallel]] to the [[material cross section]].  [[Normal stress]], on the other hand, arises from the force vector component [[perpendicular]] to the material cross section on which it acts.}}
{{term|term='''[[Shortwave radiation]]'''}}{{defn|defn=Shortwave radiation (SW) is [[radiant energy]] with wavelengths in the [[Optical spectrum|visible]] (VIS), near-[[ultraviolet radiation|ultraviolet]] (UV), and [[near-infrared]] (NIR) spectra.

There is no standard cut-off for the near-infrared range; therefore, the shortwave radiation range is also variously defined. It may be broadly defined to include all radiation with a wavelength of 0.1[[micrometre|μm]] and 5.0μm or narrowly defined so as to include only radiation between 0.2μm and 3.0μm.

There is little radiation flux (in terms of [[Irradiance|W/m<sup>2</sup>]]) to the Earth's surface below 0.2μm or above 3.0μm, although photon flux remains significant as far as 6.0μm, compared to shorter wavelength fluxes.  [[UV-C]] radiation spans from 0.1μm to .28μm, [[UV-B]] from 0.28μm to 0.315μm, [[UV-A]] from 0.315μm to 0.4μm, the visible spectrum from 0.4μm to 0.7μm, and [[near-infrared|NIR]] arguably from 0.7μm to 5.0μm, beyond which the infrared is thermal.<ref>However, the definition of thermal infrared may start at wavelengths as short as 1.1μm (longer than which optical instruments have difficulty measuring) or anywhere between 2.0μm and 4.0μm, depending on the method of measurement and its purpose.</ref>

Shortwave radiation is distinguished from [[longwave]] radiation. Downward shortwave radiation is sensitive to [[solar zenith angle]], [[cloud cover]].<ref>[https://dx.doi.org/10.1016/j.rse.2012.04.006 L. Chen, G. Yan, T. Wang, H. Ren, J. Calbó, J. Zhao, R. McKenzie (2012), Estimation of surface shortwave radiation components under all sky conditions: Modeling and sensitivity analysis, Remote Sensing of Environment, 123: 457–469.]</ref>}}
{{term|term='''[[SI units]]'''}}{{defn|defn=The  '''International System of Units''' ('''SI''', abbreviated from the [[French language|French]] ''{{lang|fr|Système international (d'unités)}}'') is the modern form of the [[metric system]]. It is the only [[system of measurement]] with an official status in nearly every country in the world. It comprises a [[Coherence (units of measurement)|coherent]] system of [[units of measurement]] starting with seven [[SI base unit|base unit]]s, which are the [[second]] (the unit of [[time]] with the symbol s), [[metre]] ([[length]], m), [[kilogram]] ([[mass]], kg), [[ampere]] ([[electric current]], A), [[kelvin]] ([[thermodynamic temperature]], K), [[Mole (unit)|mole]] ([[amount of substance]], mol), and [[candela]] ([[luminous intensity]], cd). The system allows for an unlimited number of additional units, called [[SI derived unit|derived units]], which can always be represented as products of powers of the base units.{{efn|For example, the SI unit of [[velocity]] is the metre per second, m⋅s<sup>−1</sup>; of [[acceleration]] is the metre per second squared, m⋅s<sup>−2</sup>; etc.}} Twenty-two derived units have been provided with special names and symbols.{{efn|For example the [[Newton (unit)|newton]] (N), the unit of [[force]], equivalent to kg⋅m⋅s<sup>−2</sup>; the [[joule]] (J), the unit of [[energy]], equivalent to kg⋅m<sup>2</sup>⋅s<sup>−2</sup>, etc. The most recently named derived unit, the [[katal]], was defined in 1999.}} The seven base units and the 22 derived units with special names and symbols may be used in combination to express other derived units,{{efn|For example, the recommended unit for the [[Electric field|electric field strength]] is the volt per metre, V/m, where the [[volt]] is the derived unit for [[Voltage|electric potential difference]]. The volt per metre is equal to kg⋅m⋅s<sup>−3</sup>⋅A<sup>−1</sup> when expressed in terms of base units.}} which are adopted to facilitate measurement of diverse quantities. The SI also provides twenty [[Metric prefix|prefix]]es to the unit names and unit symbols that may be used when specifying power-of-ten (i.e. decimal) multiples and sub-multiples of SI units. The SI is intended to be an evolving system; units and prefixes are created and unit definitions are modified through international agreement as the technology of [[measurement]] progresses and the precision of measurements improves.}} 
{{term|term='''[[Signal processing]]'''}}{{defn|defn=Is an [[electrical engineering]] subfield that focuses on analysing, modifying, and synthesizing [[signal]]s such as [[audio signal processing|sound]], [[image processing|images]], and scientific measurements.<ref>{{cite journal|last=Sengupta|first=Nandini|author2=Sahidullah, Md|author3=Saha, Goutam|date=August 2016|title=Lung sound classification using cepstral-based statistical features|journal=Computers in Biology and Medicine|volume=75|issue=1|pages=118–129|doi=10.1016/j.compbiomed.2016.05.013|pmid=27286184}}</ref> Signal processing techniques can be used to improve transmission, storage efficiency and subjective quality and to also emphasize or detect components of interest in a measured signal.<ref>{{cite book|title=Discrete-Time Signal Processing|author=Alan V. Oppenheim and Ronald W. Schafer|publisher=Prentice Hall|year=1989|isbn=0-13-216771-9|page=1}}</ref>}}
{{term|term='''[[Simple machine]]'''}}{{defn|defn=Is a mechanical device that changes the direction or magnitude of a [[force]].<ref name="Paul-Roy-Mukherjee-2005">{{Citation |last1=Paul |first1=Akshoy |last2=Roy |first2=Pijush |last3=Mukherjee |first3=Sanchayan |title=Mechanical sciences: engineering mechanics and strength of materials |year=2005 |publisher=Prentice Hall of India |isbn=978-81-203-2611-8 |page=215 |postscript=.}}</ref> In general, they can be defined as the simplest mechanisms that use [[mechanical advantage]] (also called [[lever]]age) to multiply force.<ref name="Asimov1988">{{Citation |last=Asimov |first=Isaac |title=Understanding Physics |year=1988 |publisher=Barnes & Noble |location=New York |isbn=978-0-88029-251-1 |url=https://books.google.com/books?id=pSKvaLV6zkcC&q=Asimov+simple+machine&pg=PA88 |page=88 |postscript=.}}</ref> Usually the term refers to the six classical simple machines that were defined by [[Renaissance]] scientists:<ref name="Anderson">{{cite book
  |last=Anderson
  |first=William Ballantyne
  |title=Physics for Technical Students: Mechanics and Heat
  |year=1914
  |publisher=McGraw Hill
  |location=New York
  |url=https://archive.org/details/bub_gb_Pa0IAAAAIAAJ/page/n131
  |access-date=2008-05-11
  |pages=112}}</ref><ref name="Britannica1773">{{cite encyclopedia
  | title = Mechanics
  | encyclopedia = Encyclopædia Britannica
  | volume = 3
  | pages = 44
  | publisher = John Donaldson
  | date =1773
  | url = https://books.google.com/books?id=Ow8UAAAAQAAJ&q=%22simple+machine%22+%22mechanical+powers%22+lever+screw+inclined+plane+wedge+wheel+pulley&pg=PA44
  | access-date = 5 April 2020}}</ref><ref name="Morris">{{cite book
 | last1  = Morris
 | first1 = Christopher G. 
 | title  = Academic Press Dictionary of Science and Technology
 | publisher = Gulf Professional Publishing
 | date   = 1992
 | pages  = 1993
 | url    = https://books.google.com/books?id=nauWlPTBcjIC&q=%22simple+machine%22&pg=PA1993
 | isbn   = 9780122004001
 }}</ref>

* [[Lever]]
* [[Wheel and axle]]
* [[Pulley]]
* [[Inclined plane]]
* [[Wedge (mechanical device)|Wedge]]
* [[Screw (simple machine)|Screw]]}}
{{term|term='''[[Siphon]]'''}}{{defn|defn=A closed tube that conveys liquids between two levels without pumping.}}
{{term|term='''[[Solid mechanics]]'''}}{{defn|defn=Also known as '''mechanics of solids''', is the branch of [[continuum mechanics]] that studies the behavior of [[solid]] materials, especially their motion and [[deformation (mechanics)|deformation]] under the action of [[force]]s, [[temperature]] changes, [[phase (chemistry)|phase]] changes, and other external or internal agents.}}
{{term|term='''[[Solid-state physics]]'''}}{{defn|defn=Is the study of rigid [[matter]], or [[solid]]s, through methods such as [[quantum mechanics]], [[crystallography]], [[electromagnetism]], and [[metallurgy]].  It is the largest branch of [[condensed matter physics]]. Solid-state physics studies how the large-scale properties of solid materials result from their [[atom]]ic-scale properties.   Thus,  solid-state physics forms a theoretical basis of [[materials science]].  It also has direct applications, for example in the technology of [[transistor]]s and [[semiconductor]]s.}}
{{term|term='''[[Solid solution strengthening]]'''}}{{defn|defn=Is a type of [[alloy]]ing that can be used to improve the [[Strength of materials|strength]] of a pure metal. The technique works by adding atoms of one element (the alloying element) to the crystalline lattice of another element (the base metal), forming a [[solid solution]]. The local nonuniformity in the lattice due to the alloying element makes plastic deformation more difficult by impeding [[dislocation]] motion through stress fields. In contrast, alloying beyond the solubility limit can form a second phase, leading to strengthening via other mechanisms (e.g. the [[Precipitation hardening|precipitation]] of [[intermetallic]] compounds).}}
{{term|term='''[[Solubility]]'''}}{{defn|defn=Is the property of a [[solid]], [[liquid]] or [[gas]]eous [[chemical substance]] called ''[[solute]]'' to dissolve in a solid, liquid or gaseous [[solvent]]. The solubility of a substance fundamentally depends on the [[Physical property|physical]] and [[Chemical property|chemical properties]] of the solute and solvent as well as on temperature, pressure and presence of other chemicals (including changes to the [[pH]]) of the solution. The extent of the solubility of a substance in a specific solvent is measured as the saturation [[concentration]], where adding more solute does not increase the concentration of the solution and begins to precipitate the excess amount of solute.}}
{{term|term='''[[Solubility equilibrium]]'''}}{{defn|defn=Is a type of [[dynamic equilibrium]] that exists when a [[chemical compound]] in the solid state is in [[chemical equilibrium]] with a [[Solution (chemistry)|solution]] of that compound. The solid may dissolve unchanged, with dissociation or with chemical reaction with another constituent of the solution, such as acid or alkali. Each solubility equilibrium is characterized by a temperature-dependent ''solubility product'' which functions like an  [[equilibrium constant]]. Solubility equilibria are important in pharmaceutical, environmental and many other scenarios.}}
{{term|term='''[[Sound]]'''}}{{defn|defn=In [[physics]], sound is a [[vibration]] that propagates as an [[acoustic wave]], through a [[transmission medium]] such as a gas, liquid or solid.}}
{{term|term='''[[Special relativity]]'''}}{{defn|defn=In [[physics]], the '''special theory of relativity''', or '''special relativity''' for short, is a scientific theory regarding the relationship between [[Spacetime|space and time]]. In [[Albert Einstein]]'s original treatment, the theory is based on two [[Axiom|postulate]]s:<ref>Albert Einstein (1905) "Zur Elektrodynamik bewegter Körper", Annalen der Physik 17: 891; English translation On the Electrodynamics of Moving Bodies by George Barker Jeffery and Wilfrid Perrett (1923); Another English translation On the Electrodynamics of Moving Bodies by Megh Nad Saha (1920).</ref><ref>{{Cite book | last = Griffiths | first = David J. | title = Introduction to Electrodynamics | title-link = Introduction to Electrodynamics | publisher = Pearson | year = 2013 | isbn = 978-0-321-85656-2 | edition = 4th | at = Chapter 12 | chapter =  Electrodynamics and Relativity | author-link = David J. Griffiths}}</ref><ref>{{Cite book | last = Jackson | first = John D. | title = Classical Electrodynamics | title-link = Classical Electrodynamics (book) | publisher = John Wiley & Sons, Inc. | year = 1999 | isbn = 0-471-30932-X | edition = 3rd | at = Chapter 11 |chapter = Special Theory of Relativity | author-link = John David Jackson (physicist)}}</ref>
# The [[laws of physics]] are [[Invariant (physics)|invariant]] (that is, identical) in all [[Inertial frame of reference|inertial frames of reference]] (that is, frames of reference with no [[acceleration]]).
# The [[speed of light]] in [[vacuum]] is the same for all observers, regardless of the motion of the light source or observer.}}
{{term|term='''[[Specific heat]]'''}}{{defn|defn=The amount of energy required to change the temperature of a unit mass of substance by one degree.}}
{{term|term='''[[Specific gravity]]'''}}{{defn|defn=The ratio between the mass density of a substance to that of water.}} 
{{term|term='''[[Specific volume]]'''}}{{defn|defn=The volume of a unit mass of a substance.}}
{{term|term='''[[Specific weight]]'''}}{{defn|defn=The weight of a substance per unit volume.}} 
{{term|term='''[[Spontaneous combustion]]'''}}{{defn|defn=Spontaneous combustion or '''spontaneous ignition''' is a type of [[combustion]] which occurs by self-heating (increase in temperature due to [[Exothermic reaction|exothermic internal reactions]]), followed by [[thermal runaway]] (self heating which rapidly accelerates to high temperatures) and finally, [[autoignition]].<ref>{{cite book|last=Babrauskas|first=Vytenis|title=Ignition Handbook|year=2003|publisher=Society of Fire Protection Engineerslocation=Boston p.369|isbn=978-0-9728111-3-2}}</ref>}}
{{term|term='''[[Stagnation pressure]]'''}}{{defn|defn=In [[fluid dynamics]], stagnation pressure (or '''pitot pressure''') is the [[static pressure]] at a [[stagnation point]] in a fluid flow.<ref name=Clancy3.5>Clancy, L.J., ''Aerodynamics'', Section 3.5</ref> At a stagnation point the fluid velocity is zero. In an incompressible flow, stagnation pressure is equal to the sum of the free-stream [[static pressure]] and the free-stream [[dynamic pressure]].<ref>[http://scienceworld.wolfram.com/physics/StagnationPressure.html Stagnation Pressure] at Eric Weisstein's World of Physics (Wolfram Research)</ref>}}
{{term|term='''[[Standard electrode potential]]'''}}{{defn|defn=.}}
{{term|term='''[[State of matter]]'''}}{{defn|defn=In [[physics]], a state of matter is one of the distinct forms in which [[matter]] can exist. Four states of matter are observable in everyday life: [[solid]], [[liquid]], [[gas]], and [[Plasma (physics)|plasma]]. Many intermediate states are known to exist, such as [[liquid crystal]], and some states only exist under extreme conditions, such as [[Bose–Einstein condensate]]s, [[neutron-degenerate matter]], and [[quark–gluon plasma]], which only occur, respectively, in situations of extreme cold, extreme density, and extremely high energy. For a complete list of all exotic states of matter, see the [[list of states of matter]].}}
{{term|term='''[[Statics]]'''}}{{defn|defn=The study of forces in a non-moving, rigid body.}} 
{{term|term='''[[Statistics]]'''}}{{defn|defn=Is the discipline that concerns the collection, organization, analysis, interpretation, and presentation of [[data]].<ref name=ox>{{cite book | title=Oxford Reference|chapter = Statistics|date = January 2008|publisher = Oxford University Press|isbn = 978-0-19-954145-4|url=https://www.oxfordreference.com/view/10.1093/acref/9780199541454.001.0001/acref-9780199541454-e-1566?rskey=nxhBLl&result=1979}}</ref><ref>{{cite encyclopedia |first=Jan-Willem |last=Romijn |year=2014 |title=Philosophy of statistics |encyclopedia=Stanford Encyclopedia of Philosophy |url=http://plato.stanford.edu/entries/statistics/}}</ref><ref>{{cite web | title=Cambridge Dictionary | url=https://dictionary.cambridge.org/dictionary/english/statistics}}</ref> In applying statistics to a scientific, industrial, or social problem, it is conventional to begin with a [[statistical population]] or a [[statistical model]] to be studied. Populations can be diverse groups of people or objects such as "all people living in a country" or "every atom composing a crystal". Statistics deals with every aspect of data, including the planning of data collection in terms of the design of [[statistical survey|surveys]] and [[experimental design|experiments]].<ref name=Dodge>Dodge, Y. (2006) ''The Oxford Dictionary of Statistical Terms'', Oxford University Press. {{isbn|0-19-920613-9}}</ref>}}
{{term|term='''[[Steam table]]'''}}{{defn|defn=Thermodynamic data table containing steam or water properties .<ref>[https://www.chegg.com/homework-help/definitions/steam-tables-5 Chegg Study chegg.com] Retrieved August 2021</ref>}}
{{term|term='''[[Stefan–Boltzmann law]]'''}}{{defn|defn=The Stefan–Boltzmann law describes the power radiated from a [[black body]] in terms of its [[thermodynamic temperature|temperature]].  Specifically, the Stefan–Boltzmann law states that the total [[energy]] radiated per unit [[area|surface area]] of a [[black body]] across [[Black-body radiation#Spectrum|all wavelengths]] per unit [[time]] <math> j^{\star}</math> (also known as the black-body ''[[radiant emittance]]'') is directly [[Proportionality (mathematics)|proportional]] to the fourth power of the black body's [[thermodynamic temperature]] ''T'':

:<math> j^{\star} = \sigma T^{4}.</math>

The [[constant of proportionality]] ''σ'', called the [[Stefan–Boltzmann constant]], is derived from other known [[physical constant]]s. [[2019 redefinition of the SI base units|Since 2019]], the value of the constant is

:<math>
\sigma=\frac{2\pi^5 k^4}{15c^2h^3} = 5.670374\ldots\times 10^{-8}\, \mathrm{W\, m^{-2}\,K^{-4}},
</math>

where ''k'' is the [[Boltzmann constant]], ''h'' is the [[Planck constant]], and ''c'' is [[speed of light|the speed of light in vacuum]]. The [[radiance]] from a specified angle of view (watts per square metre per [[steradian]]) is given by
:<math> L = \frac{j^{\star}}\pi = \frac\sigma\pi T^{4}.</math>

A body that does not absorb all incident radiation (sometimes known as a grey body) emits less total energy than a black body and is characterized by an [[emissivity]], <math>\varepsilon < 1</math>:

:<math> j^{\star} = \varepsilon\sigma T^{4}.</math>

The radiant emittance <math> j^{\star}</math> has [[dimensional analysis#Definition|dimensions]] of [[energy flux]] (energy per unit time per unit area), and the [[SI units]] of measure are [[joule]]s per second per square metre, or equivalently, [[watt]]s per square metre. The SI unit for absolute temperature ''T'' is the [[kelvin]].  ''<math>\varepsilon</math>'' is the [[emissivity]] of the grey body; if it is a perfect blackbody, <math>\varepsilon=1</math>. In the still more general (and realistic) case, the emissivity depends on the wavelength, <math>\varepsilon=\varepsilon(\lambda)</math>.

To find the total [[Power (physics)|power]] radiated from an object, multiply by its surface area, <math>A</math>:

:<math> P= A j^{\star} = A \varepsilon\sigma T^{4}.</math>

Wavelength- and subwavelength-scale particles,<ref name="Bohren">
{{cite book
 |last1=Bohren |first1=Craig F.
 |last2=Huffman |first2=Donald R.
 |year=1998
 |title=Absorption and scattering of light by small particles
 |url=https://books.google.com/books?id=ib3EMXXIRXUC
 |publisher=Wiley
 |isbn=978-0-471-29340-8
 |pages=123–126
}}</ref> [[metamaterial]]s,<ref>
{{Cite book
 |last1=Narimanov |first1=Evgenii E.
 |last2=Smolyaninov |first2=Igor I.
 |year=2012
 |chapter=Beyond Stefan–Boltzmann Law: Thermal Hyper-Conductivity
 |title=Conference on Lasers and Electro-Optics 2012
 |series=OSA Technical Digest
 |publisher=Optical Society of America
 |pages=QM2E.1
 |doi=10.1364/QELS.2012.QM2E.1
 |isbn=978-1-55752-943-5
|citeseerx=10.1.1.764.846
 |s2cid=36550833
 }}</ref> and other nanostructures are not subject to ray-optical limits and may be designed to exceed the Stefan–Boltzmann law.}}
{{term|term='''[[Stewart platform]]'''}}{{defn|defn=Is a type of [[parallel manipulator]] that has six [[prismatic joint|prismatic actuators]], commonly [[hydraulic jack]]s or electric [[linear actuator]]s, attached in pairs to three positions on the platform's baseplate, crossing over to three mounting points on a top plate. All 12 connections are made via [[universal joint]]s. Devices placed on the top plate can be moved in the [[six degrees of freedom]] in which it is possible for a freely-suspended body to move: three linear movements x, y, z (lateral, longitudinal, and vertical), and the three rotations (pitch, roll, and yaw).}} 
{{term|term='''[[Stiffness]]'''}}{{defn|defn=Is the extent to which an object resists [[Deformation (mechanics)|deformation]] in response to an applied [[force]].<ref>{{cite journal
| title = Stiffness--an unknown world of mechanical science?
| journal = Injury
| author = Baumgart F.
| year = 2000
| volume = 31
| pages = 14–84
| publisher = Elsevier
| quote = "Stiffness" = "Load" divided by "Deformation"
| doi=10.1016/S0020-1383(00)80040-6| pmid = 10853758
}}</ref>

The complementary concept is '''flexibility''' or pliability: the more flexible an object is, the less stiff it is.<ref>{{citation |page=126 |chapter=Stiffness and flexibility |title=200 science investigations for young students |author=Martin Wenham |year=2001 |publisher=SAGE Publications |isbn=978-0-7619-6349-3}}</ref>}}
{{term|term='''[[Stoichiometry]]'''}}{{defn|defn=Refers to the relationship between the quantities of [[reactant]]s and [[Product (chemistry)|products]] before, during, and following [[chemical reaction]]s.

Stoichiometry is founded on the [[law of conservation of mass]] where the total mass of the reactants equals the total mass of the products, leading to the insight that the relations among quantities of reactants and products typically form a ratio of positive integers.   This means that if the amounts of the separate reactants are known, then the amount of the product can be calculated. Conversely, if one reactant has a known quantity and the quantity of the products can be empirically determined, then the amount of the other reactants can also be calculated.}}
{{term|term='''[[Deformation (mechanics)|Strain]]'''}}{{defn|defn=.}}
{{term|term='''[[Work hardening|Strain hardening]]'''}}{{defn|defn='''Work hardening''', also known as strain hardening, is the [[strength of materials|strengthening]] of a metal or polymer by [[plastic deformation]]. Work hardening may be desirable, undesirable, or inconsequential, depending on the context.

This strengthening occurs because of [[dislocation]] movements and dislocation generation within the [[crystal structure]] of the material.<ref name="Degarmo 2003 60">{{harvnb|Degarmo|Black|Kohser|2003|p=60}}.</ref> Many non-brittle metals with a reasonably high [[melting point]] as well as several polymers can be strengthened in this fashion.<ref>{{Citation|last1=Van Melick|first1=H. G. H.|last2= Govaert|first2=L. E.|last3=Meijer|first3=H. E. H.|year=2003|title= On the origin of strain hardening in glassy polymers|journal= Polymer|volume=44|number=8|pages= 2493–2502|doi=10.1016/s0032-3861(03)00112-5}}</ref> Alloys not amenable to [[heat treatment]], including low-carbon steel, are often work-hardened. Some materials cannot be work-hardened at low temperatures, such as [[indium]],<ref>{{Citation|last=Swenson|first= C. A.|year=1955|title=Properties of Indium and Thallium at low temperatures|journal=Physical Review|volume=100|number=6|pages=1607–1614|doi=10.1103/physrev.100.1607|bibcode= 1955PhRv..100.1607S}}</ref> however others can be strengthened only via work hardening, such as pure copper and aluminum.<ref>{{harvnb|Smith|Hashemi|2006|p=246}}.</ref>}}
{{term|term='''[[Strength of materials]]'''}}{{defn|defn=The field of strength of materials, also called '''mechanics of materials''', typically refers to various methods of calculating the [[stress (physics)|stresses]] and [[strain (physics)|strains]] in structural members, such as beams, columns, and shafts. The methods employed to predict the response of a structure under loading and its susceptibility to various failure modes takes into account the properties of the materials such as its [[yield strength]], [[ultimate strength]], [[Young's modulus]], and [[Poisson's ratio]]. In addition, the mechanical element's macroscopic properties (geometric properties) such as its length, width, thickness, boundary constraints and abrupt changes in geometry such as holes are considered.}}
{{term|term='''[[Stress (mechanics)|Stress]]'''}}{{defn|defn=In [[continuum mechanics]], stress is a [[physical quantity]] that expresses the internal [[force]]s that neighbouring [[particle]]s of a continuous material exert on each other, while [[deformation (mechanics)#Strain|strain]] is the measure of the deformation of the material. For example, when a [[solid]] vertical bar is supporting an overhead [[weight]], each particle in the bar pushes on the particles immediately below it. When a [[liquid]] is in a closed container under [[pressure]], each particle gets pushed against by all the surrounding particles.  The container walls and the [[pressure]]-inducing surface (such as a piston) push against them in (Newtonian) [[reaction force|reaction]]. These macroscopic forces are actually the net result of a very large number of [[intermolecular force]]s and [[statistical mechanics|collision]]s between the particles in those [[molecule]]s. Stress is frequently represented by a lowercase Greek letter sigma (''σ'').}}
{{term|term='''[[Stress–strain analysis]]'''}}{{defn|defn=Stress–strain analysis (or '''stress analysis''') is an [[engineering]] discipline that uses many methods to determine the [[stress (mechanics)|stresses]] and [[strain (mechanics)|strains]] in materials and structures subjected to [[force]]s. In [[continuum mechanics]], stress is a [[physical quantity]] that expresses the internal [[force]]s that neighboring [[particle]]s of a [[continuum mechanics|continuous material]] exert on each other, while strain is the measure of the deformation of the material.

In simple terms we can define stress as the force of resistance per unit per unit area, offered by a body against deformation. Stress is the ratio of force over area (S =R/A, where S is the stress, R is the internal resisting force and A is the cross-sectional area). Strain is the ratio of change in length to the original length, when a given body is subjected to some external force (Strain= change in length÷the original length).}}
{{term|term='''[[Stress–strain curve]]'''}}{{defn|defn=In engineering and [[materials science]], a stress–strain curve for a material gives the relationship between [[stress (mechanics)|stress]] and [[Deformation (physics)#Strain|strain]]. It is obtained by gradually applying [[Structural load|load]] to a test coupon and measuring the [[Deformation (engineering)|deformation]], from which the stress and strain can be determined (see [[tensile testing]]). These curves reveal many of the [[List of materials properties|properties of a material]], such as the [[Young's modulus]], the [[yield strength]] and the [[ultimate tensile strength]].}}
{{term|term='''[[Structural analysis]]'''}}{{defn|defn=Is the determination of the effects of [[structural load|load]]s on physical [[structure]]s and their [[Structural engineering#Structural elements|components]].
Structures subject to this type of [[analysis]] include all that must withstand loads, such as buildings, bridges, aircraft and ships.  Structural analysis employs the fields of [[applied mechanics]], [[materials science]] and [[applied mathematics]] to compute a structure's [[deformation (engineering)|deformation]]s, internal [[force]]s, [[stress analysis|stress]]es, support reactions, accelerations, and [[structural stability|stability]]. The results of the analysis are used to verify a structure's fitness for use, often precluding [[physical test]]s. Structural analysis is thus a key part of the [[structural engineering|engineering design of structures]].<ref>[https://www.sciencedirect.com/topics/engineering/structural-analysis "Science Direct: Structural Analysis"] {{webarchive|url=https://web.archive.org/web/20210516014830/https://www.sciencedirect.com/topics/engineering/structural-analysis |date=2021-05-16 }}</ref>}} 
{{term|term='''[[Structural load]]'''}}{{defn|defn=A structural load or '''structural action''' is a [[force]], [[Deformation (engineering)|deformation]], or [[acceleration]] applied to [[Structural engineering#Structural elements|structural elements]].<ref>{{cite book|title=ASCE/SEI 7-05 Minimum Design Loads for Buildings and Other Structures|year=2006|publisher=American Society of Civil Engineers|isbn=0-7844-0809-2|pages=1}}</ref><ref>{{cite book|title=Eurocode 0: Basis of structural design EN 1990 |year=2002|publisher=European Committee for Standardization|location=Bruxelles|chapter=1.5.3.1}}</ref> A load causes [[stress (physics)|stress]], [[deformation (engineering)|deformation]], and [[displacement (vector)|displacement]] in a [[structure]]. [[Structural analysis]], a discipline in [[engineering]], analyzes the effects loads on structures and structural elements. Excess load may cause [[structural failure]], so this should be considered and controlled during the design of a structure. Particular  mechanical structures—such as [[aircraft]], [[satellite]]s, [[rocket]]s, [[space station]]s, [[ship]]s, and [[submarine]]s—are subject to their own particular structural loads and actions.<ref>{{cite book|title=Mark's Standard Handbook for Mechanical Engineers|year=1996 |publisher=McGraw-Hill|isbn=0-07-004997-1|edition=10th|editor=Avallone, E.A. |editor2= Baumeister, T.|pages=11–42}}</ref> Engineers often evaluate structural loads based upon published [[regulation]]s, [[contract]]s, or [[specification]]s.  Accepted [[technical standard]]s are used for [[acceptance testing]] and [[inspection]].}}
{{term|term='''[[Sublimation (phase transition)|Sublimation]]'''}}{{defn|defn=Is the transition of a substance directly from the [[solid]] to the [[gas]] state,<ref>{{cite Merriam-Webster|Sublimate}}</ref> without passing through the liquid state.<ref>{{cite book |last1=Whitten |first1=Kenneth W. |last2=Gailey |first2=Kenneth D. |last3=Davis |first3=Raymond E. |title=General chemistry |url=https://archive.org/details/generalchemistry00whit_0 |url-access=registration |date=1992 |publisher=Saunders College Publishing |isbn=0-03-072373-6 |page=[https://archive.org/details/generalchemistry00whit_0/page/475 475] |edition=4th}}</ref> Sublimation is an [[endothermic process]] that occurs at temperatures and pressures below a substance's [[triple point]] in its [[phase diagram]], which corresponds to the lowest pressure at which the substance can exist as a liquid. The reverse process of sublimation is [[deposition (phase transition)|deposition]] or desublimation, in which a substance passes directly from a gas to a solid phase.<ref name="DepositionDef">{{cite journal |title=Controlling condensation and frost growth with chemical micropatterns |first1=Jonathan B. |last1=Boreyko |first2=Ryan R. |last2=Hansen |first3=Kevin R. |last3=Murphy |first4=Saurabh |last4=Nath |first5=Scott T. |last5=Retterer |first6=C. Patrick |last6=Collier |journal=Scientific Reports |year=2016 |volume=6 |pages=19131 |doi=10.1038/srep19131 |pmid=26796663 |pmc=4726256 |bibcode=2016NatSR...619131B}}</ref> Sublimation has also been used as a generic term to describe a solid-to-gas transition (sublimation) followed by a gas-to-solid transition ([[deposition (phase transition)|deposition]]).<ref>{{Dictionary.com|Sublime}}</ref> While [[vaporization]] from liquid to gas occurs as [[evaporation]] from the surface if it occurs below the boiling point of the liquid, and as [[boiling]] with formation of bubbles in the interior of the liquid if it occurs at the boiling point, there is no such distinction for the solid-to-gas transition which always occurs as sublimation from the surface.}}
{{term|term='''[[Subsumption architecture]]'''}}{{defn|defn=Is a reactive [[robotic architectures|robotic architecture]] heavily associated with [[behavior-based robotics]] which was very popular in the 1980s and 90s.  The term was introduced by [[Rodney Brooks]] and colleagues in 1986.<ref name=Brooks1986a>{{cite journal
 | doi = 10.1109/JRA.1986.1087032
 | author = Brooks, R.
 | year = 1986
 | title = A robust layered control system for a mobile robot
 | journal = IEEE Journal of Robotics and Automation
 | volume = 2
 | issue = 1
 | pages = 14–23
 | hdl = 1721.1/6432
 | s2cid = 10542804
 | hdl-access = free
 }}</ref><ref name=Brooks1986b>{{cite conference
 | author = Brooks, R.
 | year = 1986
 | title = Asynchronous distributed control system for a mobile robot.
 | book-title = SPIE Conference on Mobile Robots
 | pages = 77–84
 | url = http://www.csa.com/partners/viewrecord.php?requester=gs&collection=TRD&recid=1481881CI
 }}{{Dead link|date=May 2023 |bot=InternetArchiveBot |fix-attempted=yes }}</ref><ref>Brooks, R. A., "A Robust Programming Scheme for a Mobile Robot", Proceedings of NATO Advanced Research Workshop on Languages for Sensor-Based Control in Robotics, Castelvecchio Pascoli, Italy, September 1986.</ref>  Subsumption has been widely influential in [[autonomous robotics]] and elsewhere in [[real-time computing|real-time]] [[artificial intelligence|AI]].}} 
{{term|term='''[[Surface tension]]'''}}{{defn|defn=Is the tendency of [[liquid]] surfaces at rest to shrink into the minimum [[surface area]] possible. Surface tension is what allows objects with a higher density than water to float on a water surface without becoming even partly submerged.}}
{{term|term='''[[Superconductivity]]'''}}{{defn|defn=Is a set of physical properties observed in certain materials where [[Electrical resistance and conductance|electrical resistance]] vanishes and [[magnetic field|magnetic flux fields]] are expelled from the material. Any material exhibiting these properties is a '''superconductor'''. Unlike an ordinary metallic [[electrical conductor|conductor]], whose resistance decreases gradually as its temperature is lowered even down to near [[absolute zero]], a superconductor has a characteristic [[Phase transition|critical temperature]] below which the resistance drops abruptly to zero. An [[electric current]] through a loop of [[superconducting wire]] can persist indefinitely with no power source.<ref>{{cite book
  | author =John Bardeen
  | author2 = Leon Cooper
  | author3 = J. R. Schriffer
  | title = Theory of Superconductivity
  | journal = Physical Review
  | volume = 108
  | issue = 5
  | pages = 1175
  | date = December 1, 1957
  | url = https://books.google.com/books?id=_QKPGDG-cuAC&q=%22persist+indefinitely&pg=PA76
  | doi = 10.1103/physrev.108.1175
  | access-date = June 6, 2014|bibcode = 1957PhRv..108.1175B | isbn = 978-0-677-00080-0
  | s2cid = 73661301
 }} reprinted in Nikolaĭ Nikolaevich Bogoliubov (1963) ''The Theory of Superconductivity, Vol. 4'', CRC Press, {{ISBN|0677000804}}, p. 73</ref><ref name="Daintith">{{cite book
 | author = John Daintith
 | title = The Facts on File Dictionary of Physics
 | publisher = Infobase Publishing
 | edition = 4th
 | date = 2009
 | pages = 238
 | url = https://books.google.com/books?id=VdEVdJo3CDgC&pg=PA238
 | isbn = 978-1-4381-0949-7  }}</ref><ref name="Gallop">{{cite book
 |author=John C. Gallop
 |date=1990
 |title=SQUIDS, the Josephson Effects and Superconducting Electronics
 |url=https://books.google.com/books?id=ad8_JsfCdKQC
 |publisher=[[CRC Press]]
 |pages=1, 20
 |isbn=978-0-7503-0051-3
}}</ref><ref name="Durrant">{{cite book
 | last1 = Durrant
 | first1 = Alan
 | title = Quantum Physics of Matter
 | publisher = CRC Press
 | date = 2000
 | pages = 102–103
 | url = https://books.google.com/books?id=F0JmHRkJHiUC&q=%22persist+indefinitely&pg=PA103
 | isbn = 978-0-7503-0721-5 }}</ref>}}
{{term|term='''[[Superhard material]]'''}}{{defn|defn=Is a material with a hardness value exceeding 40 gigapascals ([[GPa]]) when measured by the [[Vickers hardness test]].<ref>{{cite journal|last1=Wentorf|first1=R. H.|last2=Devries|first2=R. C.|last3=Bundy|first3=F. P.|title=Sintered Superhard Materials|journal=Science|volume=208|pages=873–80|date=1980|doi=10.1126/science.208.4446.873|issue=4446|pmid=17772811|s2cid=34588568}}</ref><ref>Fischer-Cripps, Anthony C. (2004) [https://books.google.com/books?id=YArOm3wI9xQC&pg=PA198 Nanoindentation]. Springer. {{ISBN|0-387-22045-3}}. p. 198</ref><ref>Veprek, S.; Zeer, A. and Riedel, R. (2000) in ''Handbook of Ceramic Hard
Materials'', R. Riedel (ed.). Wiley, Weinheim. {{ISBN|3-527-29972-6}}</ref><ref name=d1>{{cite journal|last1=Dubrovinskaia|first1=N.|last2=Dubrovinsky|first2=L.|last3=Solozhenko|first3=V. L.|title=Comment on "Synthesis of Ultra-Incompressible Superhard Rhenium Diboride at Ambient Pressure"|journal=Science|volume=318|pages=1550c|date=2007|doi=10.1126/science.1147650|issue=5856|bibcode = 2007Sci...318.1550D|pmid=18063772|doi-access=free}}</ref> They are virtually incompressible solids with high electron density and high [[Covalent bond|bond covalency]]. As a result of their unique properties, these materials are of great interest in many industrial areas including, but not limited to, [[abrasive]]s, polishing and [[Cutting tool (machining)|cutting tools]], [[disc brake]]s, and [[wear]]-resistant and protective coatings.}}
{{term|term='''[[Supersaturation]]'''}}{{defn|defn=Supersaturation occurs with a [[chemical solution]] when the concentration of a [[solute]] exceeds the concentration specified by the value equilibrium [[solubility]]. Most commonly the term is applied to a solution of a solid in a liquid. A supersaturated solution is in a [[metastable]] state; it may be brought to equilibrium by forcing the excess of solute to separate from the solution. The term can also  be applied to a mixture of gases.}}
{{glossary end}}{{Glossary of engineering: M - Z ToC}}

== T ==
{{glossary}}
{{term|term='''[[Acceleration#Tangential and centripetal acceleration|Tangential acceleration]]'''}}{{defn|defn=The velocity of a particle moving on a curved path as a [[function (mathematics)|function]] of time can be written as:
:<math>\mathbf{v}(t) = v(t) \frac{\mathbf{v}(t)}{v(t)} = v(t) \mathbf{u}_\mathrm{t}(t) , </math>

with ''v''(''t'') equal to the speed of travel along the path, and

:<math>\mathbf{u}_\mathrm{t} = \frac{\mathbf{v}(t)}{v(t)} \ , </math>

a [[Differential geometry of curves#Tangent vector|unit vector tangent]] to the path pointing in the direction of motion at the chosen moment in time. Taking into account both the changing speed ''v''(''t'') and the changing direction of '''u'''<sub>''t''</sub>, the acceleration of a particle moving on a curved path can be written using the [[chain rule]] of differentiation<ref>{{cite web|last1=Weisstein|first1=Eric W.|title=Chain Rule| url=http://mathworld.wolfram.com/ChainRule.html|website=Wolfram MathWorld| publisher=Wolfram Research| access-date=2 August 2016}}</ref> for the product of two functions of time as:

:<math>\begin{alignat}{3}
\mathbf{a} & = \frac{d \mathbf{v}}{dt} \\
           & =  \frac{dv}{dt} \mathbf{u}_\mathrm{t} +v(t)\frac{d \mathbf{u}_\mathrm{t}}{dt} \\
           & = \frac{dv }{dt} \mathbf{u}_\mathrm{t}+ \frac{v^2}{r}\mathbf{u}_\mathrm{n}\ ,
\end{alignat}</math>

where '''u'''<sub>n</sub> is the  unit (inward) [[Differential geometry of curves#Normal or curvature vector|normal vector]] to the particle's trajectory (also called ''the principal normal''), and '''r''' is its instantaneous [[Curvature#Curvature of plane curves|radius of curvature]] based upon the [[Osculating circle#Mathematical description|osculating circle]] at time ''t''. These components are called the tangential acceleration and the normal or radial acceleration (or centripetal acceleration in circular motion, see also [[circular motion]] and [[centripetal force]]).

Geometrical analysis of three-dimensional space curves, which explains tangent, (principal) normal and binormal, is described by the [[Frenet–Serret formulas]].<ref name = Andrews>{{cite book |title = Mathematical Techniques for Engineers and Scientists |author1=Larry C. Andrews |author2=Ronald L. Phillips |page = 164 |url = https://books.google.com/books?id=MwrDfvrQyWYC&q=particle+%22planar+motion%22&pg=PA164
|isbn = 978-0-8194-4506-3 |publisher = SPIE Press |year = 2003  }}</ref><ref name = Chand>{{cite book |title = Applied Mathematics |page = 337 |author1=Ch V Ramana Murthy |author2=NC Srinivas |isbn = 978-81-219-2082-7|url = https://books.google.com/books?id=Q0Pvv4vWOlQC&pg=PA337|publisher = S. Chand & Co. | year = 2001| location=New Delhi }}</ref>}}
{{term|term='''[[Technical standard]]'''}}{{defn|defn=A technical standard is an established [[norm (social)|norm]] or [[requirement]] for a repeatable technical task. It is usually a formal document that establishes uniform engineering or technical criteria, methods, processes, and practices. In contrast, a custom, [[Convention (norm)|convention]], company product, corporate standard, and so forth that becomes generally accepted and dominant is often called a [[de facto standard|''de facto'' standard]].}}
{{term|term='''[[Temperature]]'''}}{{defn|defn=Is a physical quantity that expresses hot and cold. It is the manifestation of [[thermal energy]], present in all matter, which is the source of the occurrence of [[heat]], a flow of energy, when a body is in contact with another that is colder. Temperature is [[measurement|measured]] with a [[thermometer]]. Thermometers are calibrated in various [[Conversion of units of temperature|temperature scales]] that historically have used various reference points and thermometric substances for definition. The most common scales are the [[Celsius|Celsius scale]] (formerly called ''centigrade'', denoted °C), the [[Fahrenheit|Fahrenheit scale]] (denoted °F), and the [[Kelvin|Kelvin scale]] (denoted K), the last of which is predominantly used for scientific purposes by conventions of the [[International System of Units]] (SI).}} 
{{term|term='''[[Tempering (metallurgy)]]'''}}{{defn|defn=Heat treatment to alter the crystal structure of a metal such as steel.}}
{{term|term='''[[Tensile force]]'''}}{{defn|defn=Pulling force, tending to lengthen an object.}}
{{term|term='''[[Tensile Modulus|Tensile modulus]]'''}}{{defn|defn=''Young's modulus'' <math>E</math>, the ''Young modulus'', or the [[modulus of elasticity]] in tension, is a mechanical property that measures the tensile [[stiffness]] of a [[solid]] material. It quantifies the relationship between tensile [[stress (mechanics)|stress]] <math>\sigma</math> (force per unit area) and axial [[strain (mechanics)|strain]] <math>\varepsilon</math> (proportional deformation) in the [[linear elasticity|linear elastic]] region of a material and is determined using the formula:<ref>{{cite book |title=Nature and Properties of Engineering Materials |first=D. |last=Jastrzebski |publisher=John Wiley & Sons, Inc |edition=Wiley International |year=1959}}</ref>
<math display="block">E = \frac{\sigma}{\varepsilon}</math>

Young's moduli are typically so large that they are expressed not in [[Pascal (unit)|pascals]] but in gigapascals (GPa).}}
{{term|term='''[[Tensile strength]]'''}}{{defn|defn=Ultimate tensile strength (UTS), often shortened to tensile strength (TS), ultimate strength, or <math>F_\text{tu}</math> within equations,<ref name="stressebook.com">{{cite web|url=http://www.stressebook.com/mmpds-mechanical-properties-table/|title=Generic MMPDS Mechanical Properties Table|date=6 December 2014|website=stressebook.com|access-date=27 April 2018|url-status=live|archive-url=https://web.archive.org/web/20171201200651/http://www.stressebook.com/mmpds-mechanical-properties-table/|archive-date=1 December 2017|df=dmy-all}}</ref><ref name="Degarmo 2003 31">{{harvnb|Degarmo|Black|Kohser|2003|p=31}}</ref><ref name="Smith 2006 223">{{harvnb|Smith|Hashemi|2006|p=223}}</ref> is the maximum [[stress (mechanics)|stress]] that a material can withstand while being stretched or pulled before breaking. In [[brittle failure|brittle]] materials the ultimate tensile strength is close to the [[yield point]], whereas in [[ductile]] materials the ultimate tensile strength can be higher.}}
{{term|term='''[[Tensile testing]]'''}}{{defn|defn=Tensile testing, also known as tension testing,<ref>{{cite book|last = Czichos|first = Horst|title = Springer Handbook of Materials Measurement Methods|publisher = Springer|location = Berlin|year = 2006|pages = 303–304|url = https://books.google.com/books?id=8lANaR-Pqi4C|isbn = 978-3-540-20785-6}}</ref> is a fundamental [[materials science]] and [[engineering]] test in which a sample is subjected to a controlled [[tension (physics)|tension]] until failure. Properties that are directly measured via a tensile test are [[ultimate tensile strength]], [[breaking strength]], maximum [[elongation (materials science)|elongation]] and reduction in area.<ref name="davis1">{{cite book|last = Davis|first = Joseph R.|title = Tensile testing|publisher = ASM International|year = 2004|edition = 2nd|url = https://books.google.com/books?id=5uRIb3emLY8C|isbn = 978-0-87170-806-9}}</ref> From these measurements the following properties can also be determined: [[Young's modulus]], [[Poisson's ratio]], [[yield strength]], and [[strain-hardening]] characteristics.<ref>{{harvnb|Davis|2004|p=33}}.</ref> ''Uniaxial tensile testing'' is the most commonly used for obtaining the mechanical characteristics of [[isotropy|isotropic]] materials. Some materials use ''biaxial tensile testing''. The main difference between these testing machines being how load is applied on the materials.}}
{{term|term='''[[Tension member]]'''}}{{defn|defn=Tension members are structural elements that are subjected to axial [[tensile force]]s. Examples of tension members are bracing for buildings and [[bridge]]s, [[truss]] members, and [[Wire rope|cable]]s in suspended [[roof]] systems.}}
{{term|term='''[[Thermal conduction]]'''}}{{defn|defn=Is the transfer of [[internal energy]] by microscopic collisions of particles and movement of electrons within a body. The colliding particles, which include molecules, atoms and electrons, transfer disorganized microscopic kinetic and potential energy, jointly known as internal energy. Conduction takes place in all [[phase (matter)|phases]]: solid, liquid, and gas.}}
{{term|term='''[[Thermal equilibrium]]'''}}{{defn|defn=Two [[physical system]]s are in thermal equilibrium if there is no net flow of thermal energy between them when they are connected by a path permeable to heat.  Thermal equilibrium obeys the [[zeroth law of thermodynamics]].  A system is said to be in thermal equilibrium with itself if the temperature within the system is spatially uniform and temporally constant.

Systems in [[thermodynamic equilibrium]] are always in thermal equilibrium, but the converse is not always true.  If the connection between the systems allows transfer of energy as 'change in [[internal energy]]' but does not allow transfer of matter or transfer of energy as [[work (physics)|work]], the two systems may reach thermal equilibrium without reaching thermodynamic equilibrium.}}
{{term|term='''[[Thermal radiation]]'''}}{{defn|defn=Is [[electromagnetic radiation]] generated by the [[thermal motion]] of particles in [[matter]]. All matter with a [[temperature]] greater than [[absolute zero]] emits thermal radiation. Particle motion results in [[Larmor formula|charge-acceleration]] or [[dipole]] oscillation which produces electromagnetic radiation.}}
{{term|term='''[[Thermodynamics]]'''}}{{defn|defn=Is a branch of [[physics]] that deals with [[heat]], [[Work (thermodynamics)|work]], and [[temperature]], and their relation to [[energy]], [[radiation]], and physical properties of [[matter]]. The behavior of these quantities is governed by the four [[laws of thermodynamics]] which convey a quantitative description using measurable macroscopic [[physical quantity|physical quantities]], but may be explained in terms of [[microscopic]] constituents by [[statistical mechanics]]. Thermodynamics applies to a wide variety of topics in [[science]] and [[engineering]], especially [[physical chemistry]], [[biochemistry]], [[chemical engineering]] and [[mechanical engineering]], but also in other complex fields such as [[meteorology]].}}
{{term|term='''[[Theory of relativity]]'''}}{{defn|defn=Usually encompasses two interrelated theories by [[Albert Einstein]]: [[special relativity]] and [[general relativity]], proposed and published in 1905 and 1915, respectively.<ref>{{Citation |author=Einstein A. |date=1916 |type=Translation 1920 |title=Relativity: The Special and General Theory|publisher=H. Holt and Company|location=New York|title-link=s:Relativity: The Special and General Theory }}</ref> Special relativity applies to all physical phenomena in the absence of [[gravity]]. General relativity explains the law of gravitation and its relation to other forces of nature.<ref>Einstein, Albert (November 28, 1919). [[Theory of relativity#cite note-londontimes-2|"Time, Space, and Gravitation"]] . The Times.</ref> It applies to the [[cosmological]] and astrophysical realm, including astronomy.<ref>Will, Clifford M (2010). "Relativity". Grolier Multimedia Encyclopedia. Retrieved 2010-08-01.</ref>}}
{{term|term='''[[Thévenin's theorem]]'''}}{{defn|defn=As originally stated in terms of direct-current [[resistance (electricity)|resistive]] circuits only, Thévenin's theorem states that ''"For any [[linear circuit|linear]] [[electrical network]] containing only [[voltage source]]s, [[current source]]s and [[resistance (electricity)|resistance]]s can be replaced at terminals A–B by an equivalent combination of a voltage source V<sub>th</sub> in a [[series and parallel circuit|series]] connection with a resistance R<sub>th</sub>."''

* The equivalent voltage ''V''<sub>th</sub> is the voltage obtained at terminals A–B of the network with terminals A–B [[open-circuit voltage|open circuit]]ed.
* The equivalent resistance ''R''<sub>th</sub> is the resistance that the circuit between terminals A and B would have if all ideal voltage sources in the circuit were replaced by a short circuit and all ideal current sources were replaced by an open circuit. 
* If terminals A and B are connected to one another, the current flowing from A to B will be ''V''<sub>th</sub>/''R''<sub>th</sub>. This means that ''R''<sub>th</sub> could alternatively be calculated as ''V''<sub>th</sub> divided by the short-circuit current between A and B when they are connected together.

In [[circuit theory]] terms, the theorem allows any [[one-port]] network to be reduced to a single [[voltage source]] and a single impedance.

The theorem also applies to frequency domain AC circuits consisting of [[Reactive power|reactive]] and [[resistance (electricity)|resistive]] [[Electrical impedance|impedance]]s. It means the theorem applies for AC in an exactly same way to DC except that resistances are generalized to impedances.}}
{{term|term='''[[Three-phase electric power]]'''}}{{defn|defn=Is a common method of [[alternating current]] [[electric power]] [[Electricity generation|generation]], [[Electric power transmission|transmission]], and [[Electric power distribution|distribution]].<ref>William D. Stevenson, Jr. ''Elements of Power System Analysis Third Edition'', McGraw-Hill, New York (1975). {{ISBN|0-07-061285-4}}, p. 2</ref> It is a type of [[polyphase system]] and is the most common method used by [[electrical grid]]s worldwide to transfer power. It is also used to power large [[Electric motor|motors]] and other heavy loads.}}
{{term|term='''[[Torque]]'''}}{{defn|defn=In [[physics]] and [[mechanics]], torque is the rotational equivalent of linear [[force]].<ref>Serway, R. A. and Jewett, Jr. J.W. (2003). ''Physics for Scientists and Engineers''. 6th Ed. Brooks Cole. {{ISBN|0-534-40842-7}}.</ref> It is also referred to as the '''moment''', '''moment of force''', '''rotational force''' or '''turning effect''', depending on the field of study.  The concept originated with the studies by [[Archimedes]] of the usage of [[lever]]s. Just as a linear force is a push or a pull, a torque can be thought of as a twist to an object around a specific axis. Another definition of torque is the product of the magnitude of the force and the perpendicular distance of the [[line of action]] of a force from the [[Rotation around a fixed axis|axis of rotation]]. The symbol for torque is typically <math>\boldsymbol\tau</math> or {{mvar|'''τ'''}}, the lowercase [[Greek alphabet|Greek letter]] ''[[tau]]''. When being referred to as [[moment (physics)|moment]] of force, it is commonly denoted by {{mvar|M}}.}}
{{term|term='''[[Torsional vibration]]'''}}{{defn|defn=Is angular [[vibration]] of an object—commonly a shaft along its axis of rotation.  Torsional vibration is often a concern in [[power transmission]] systems using rotating shafts or couplings where it can cause failures if not controlled. A second effect of torsional vibrations applies to passenger cars. Torsional vibrations can lead to seat vibrations or noise at certain speeds. Both reduce the comfort.}}
{{term|term='''[[Toughness]]'''}}{{defn|defn=In [[materials science]] and [[metallurgy]], toughness is the ability of a material to absorb energy and plastically deform without fracturing.<ref name=NDT>[http://www.nde-ed.org/EducationResources/CommunityCollege/Materials/Mechanical/Toughness.htm "Toughness"], [http://www.nde-ed.org/index_flash.htm NDT Education Resource Center] {{Webarchive|url=https://web.archive.org/web/20200411121541/http://www.nde-ed.org/index_flash.htm |date=2020-04-11 }}, Brian Larson, editor, 2001–2011, The Collaboration for NDT Education, [[Iowa State University]]</ref> One definition of material toughness is the amount of energy per unit volume that a material can absorb before [[rupture (engineering)|rupturing]]. This measure of toughness is different from that used for [[fracture toughness]], which describes load bearing capabilities of materials with flaws.<ref>{{Cite book|last=Askeland|first=Donald R.|url=https://www.worldcat.org/oclc/903959750|title=The science and engineering of materials|others=Wright, Wendelin J.|date=January 2015|isbn=978-1-305-07676-1|edition= Seventh|location=Boston, MA|pages=208|oclc=903959750}}</ref> It is also defined as a material's resistance to fracture when [[stress (physics)|stressed]].

Toughness requires a balance of [[Strength of materials|strength]] and [[ductility]].<ref name=NDT/>}}
{{term|term='''[[Trajectory]]'''}}{{defn|defn=A trajectory or '''flight path''' is the path that an [[physical body|object]] with [[mass]] in [[Motion (physics)|motion]] follows through [[space]] as a function of time. In [[classical mechanics]], a trajectory is defined by [[Hamiltonian mechanics]] via [[canonical coordinates]]; hence, a complete trajectory is defined by position and momentum, simultaneously.

The mass might be a [[projectile]] or a [[satellite]].<ref>{{cite book |title=The Principles of Physics |first=Rohit |last=Metha |chapter=11 |page=378}}</ref> For example, it can be an [[orbit]] — the path of a [[planet]], [[asteroid]], or [[comet]] as it travels around a [[primary (astronomy)|central mass]].

In [[control theory]], a trajectory is a time-ordered set of [[state (controls)|state]]s of a [[dynamical system]] (see e.g. [[Poincaré map]]). In [[discrete mathematics]], a trajectory is a sequence <math>(f^k(x))_{k \in \mathbb{N}}</math> of values calculated by the iterated application of a mapping <math>f</math> to an element <math>x</math> of its source.}}
{{term|term='''[[Transducer]]'''}}{{defn|defn=Is a device that [[Energy transformation|converts]] energy from one form to another. Usually a transducer converts a [[wikt:signal#Noun|signal]] in one form of energy to a signal in another.<ref>Agarwal, Anant. Foundations of Analog and Digital Electronic Circuits.Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, 2005, p. 43</ref>

Transducers are often employed at the boundaries of [[automation]], [[Measuring instrument|measurement]], and [[control system]]s, where electrical signals are converted to and from other physical quantities (energy, force, torque, light, motion, position, etc.). The process of converting one [[form of energy]] to another is known as transduction.<ref name="Audio1">{{cite book |last=Winer |first=Ethan |date=2013 |title=The Audio Expert |location=New York and London |publisher=Focal Press |chapter=Part 3 |isbn=978-0-240-82100-9}}</ref>}}
{{term|term='''[[Transformer]]'''}}{{defn|defn=Is a [[passive component]] that transfers electrical energy from one electrical circuit to another circuit, or multiple [[Electrical network|circuits]]. A varying current in any one coil of the transformer produces a varying [[magnetic flux]] in the transformer's core, which induces a varying [[electromotive force]] across any other coils wound around the same core. Electrical energy can be transferred between separate coils without a metallic (conductive) connection between the two circuits. [[Faraday's law of induction]], discovered in 1831, describes the induced voltage effect in any coil due to a changing magnetic flux encircled by the coil.}}
{{term|term='''[[Trigonometric functions]]'''}}{{defn|defn=In [[mathematics]], the trigonometric functions (also called '''circular functions''', '''angle functions''' or '''goniometric functions'''<ref>
 Klein, Christian Felix (1924) [1902]. Elementarmathematik vom höheren Standpunkt aus: Arithmetik, Algebra, Analysis (in German). 1 (3rd ed.). Berlin: J. Springer.

</ref><ref>Klein, Christian Felix (2004) [1932]. Elementary Mathematics from an Advanced Standpoint: Arithmetic, Algebra, Analysis. Translated by Hedrick, E. R.; Noble, C. A. (Translation of 3rd German ed.). Dover Publications, Inc. / The Macmillan Company. ISBN 978-0-48643480-3. Archived from the original on 2018-02-15. Retrieved 2017-08-13.</ref>) are [[real function]]s which relate an angle of a [[right-angled triangle]] to ratios of two side lengths. They are widely used in all sciences that are related to [[geometry]], such as [[navigation]], [[solid mechanics]], [[celestial mechanics]], [[geodesy]], and many others. They are among the simplest [[periodic function]]s, and as such are also widely used for studying periodic phenomena through [[Fourier analysis]].

The trigonometric functions most widely used in modern mathematics are the '''[[sine]]''', the '''cosine''', and the '''tangent'''. Their [[multiplicative inverse|reciprocal]]s are respectively the '''cosecant''', the '''secant''', and the '''cotangent''', which are less used. Each of these six trigonometric functions has a corresponding [[Inverse trigonometric functions|inverse function]], and an analog among the [[hyperbolic functions]].}}
{{term|term='''[[Trigonometry]]'''}}{{defn|defn=Is a branch of [[mathematics]] that studies relationships between side lengths and [[angle]]s of [[triangle]]s. The field emerged in the [[Hellenistic period|Hellenistic world]] during the 3rd century BC from applications of [[geometry]] to [[Astronomy|astronomical studies]].<ref>R. Nagel (ed.), ''Encyclopedia of Science'', 2nd Ed., The Gale Group (2002)</ref> The Greeks focused on the [[Ptolemy's table of chords|calculation of chords]], while mathematicians in India created the earliest-known tables of values for  trigonometric ratios (also called [[trigonometric functions]]) such as [[sine]].{{sfnp|Boyer|1991|p={{page needed|date=January 2021}}}}}}
{{term|term='''[[Trimean]]'''}}{{defn|defn=The trimean is a measure of a probability distribution's location defined as a weighted average of the distribution's median and its two quartiles}}
{{term|term='''[[Triple point]]'''}}{{defn|defn=In [[thermodynamics]], the triple point of a substance is the [[temperature]] and [[pressure]] at which the three [[Phase (matter)|phases]] ([[gas]], [[liquid]], and [[solid]]) of that substance coexist in [[thermodynamic equilibrium]].<ref name=gold>{{GoldBookRef | title=Triple point |file=T06502 |year=1994}}.</ref> It is that temperature and pressure at which the [[sublimation (phase transition)|sublimation]] curve, [[Melting|fusion]] curve and the [[vaporisation]] curve meet. For example, the triple point of [[Mercury (element)|mercury]] occurs at a temperature of {{convert|−38.83440|°C|°F}} and a pressure of 0.165 [[Milli|m]][[Pascal (unit)|Pa]].  In addition to the triple point for solid, liquid, and gas phases, a triple point may involve more than one solid phase, for substances with multiple [[polymorphism (materials science)|polymorphs]]. [[Helium-4]] is a special case that presents a triple point involving two different fluid phases ([[lambda point]]).<ref name=gold/>}}
{{term|term='''[[Trouton's rule]]'''}}{{defn|defn=Trouton's rule states that the [[entropy of vaporization]]  is almost the same value, about 85–88&nbsp;J/(K·mol), for various kinds of [[liquid]]s at their [[boiling point]]s.<ref>Compare 85&nbsp;J/(K·mol) in {{cite book |url=https://books.google.com/books?id=SpIV3J_mwiMC&pg=PA87 |title=Physical Chemistry |author=David Warren Ball|date=20 August 2002 |publisher=Cengage Learning |isbn=9780534266585 }} and 88&nbsp;J/(K·mol) in {{cite book |url=https://books.google.com/books?id=OUIaM1V3ThsC&pg=PA206 |title=Chemistry: Principles and Practice |author1=Daniel L. Reger |author2=Scott R. Goode |author3=David W. Ball |date=27 January 2009 |publisher=Cengage Learning |isbn=9780534420123 }}</ref> The entropy of vaporization is defined as the ratio between the [[enthalpy]] of vaporization and the boiling temperature. It is named after [[Frederick Thomas Trouton]].

It can be expressed as a function of the [[gas constant]] ''R'':

: <math>\Delta \bar S_\text{vap} \approx 10.5 R.</math>

A similar way of stating this ('''Trouton's ratio''') is that the [[latent heat]] is connected to [[boiling point]] roughly as

: <math>\frac{L_\text{vap}}{T_\text{boiling}} \approx 85{-}88\ \frac{\text{J}}{\text{K} \cdot \text{mol}}.</math>}}
{{term|term='''[[Truncated mean]]'''}}{{defn|defn=A truncated mean or '''trimmed mean''' is a [[Statistics|statistical]] [[Average|measure of central tendency]], much like the [[mean]] and [[median]]. It involves the calculation of the mean after discarding given parts of a [[probability distribution]] or [[Sampling (statistics)|sample]] at the high and low end, and typically discarding an equal amount of both. This number of points to be discarded is usually given as a percentage of the total number of points, but may also be given as a fixed number of points.}}
{{term|term='''[[Truss]]'''}}{{defn|defn=A truss is an assembly of ''members'' such as [[Beam (structure)|beams]], connected by ''nodes'', that creates a rigid structure.<ref>{{Cite web | url=https://www.merriam-webster.com/dictionary/truss | title=Definition of TRUSS| date=8 April 2023}}</ref>

In engineering, a truss is a [[architectural structure|structure]] that "consists of two-force members only, where the members are organized so that the assemblage as a whole behaves as a single object".<ref name="PleshaGrayCostanzo">{{cite book | last1 = Plesha | first1 = Michael E. | last2 = Gray | first2 = Gary L. | last3 = Costanzo | first3 = Francesco | title = Engineering Mechanics: Statics| edition = 2nd | year = 2013 | publisher = McGraw-Hill Companies Inc. | location = New York | isbn = 978-0-07-338029-2 | pages = 364–407}}</ref>  A "two-force member" is a structural component where force is applied to only two points.  Although this rigorous definition allows the members to have any shape connected in any stable configuration, trusses typically comprise five or more triangular units constructed with straight members whose ends are connected at joints referred to as ''[[Vertex (geometry)|nodes]]''.}}
{{term|term='''[[Turbine]]'''}}{{defn|defn=Is a rotary mechanical device that extracts [[energy]] from a [[fluid]] flow and converts it into useful [[Work (physics)|work]]. The work produced by a turbine can be used for generating electrical power when combined with a [[electric generator|generator]].<ref name = "Munson">Munson, Bruce Roy, T. H. Okiishi, and Wade W. Huebsch. "Turbomachines." Fundamentals of Fluid Mechanics. 6th ed. Hoboken, NJ: J. Wiley & Sons, 2009. Print.</ref> A turbine is a [[turbomachinery|turbomachine]] with at least one moving part called a rotor assembly, which is a shaft or drum with [[Turbine blade|blades]] attached. Moving fluid acts on the blades so that they move and impart rotational energy to the rotor. Early turbine examples are [[windmill]]s and [[waterwheel]]s. [[Gas turbine|Gas]], [[steam turbine|steam]], and [[water turbine|water]] turbines have a casing around the blades that contains and controls the working fluid.}}
 {{term|term='''[[Turbomachinery]]'''}}{{defn|defn=Turbomachinery, in [[mechanical engineering]], describes [[machine]]s that transfer [[energy]] between a [[rotor (turbine)|rotor]] and a [[fluid]], including both [[turbines]] and [[gas compressor|compressors]].  While a turbine transfers energy from a fluid to a rotor, a compressor transfers energy from a rotor to a fluid.<ref name="Logan1">Logan, Earl. "Handbook of turbomachinery". 1995. Marcel Deckker.</ref><ref name="Tamili1">Vandad Talimi (Original author unknown). "Mechanical Equipment and Systems". 2013. Memorial University of Newfoundland. http://www.engr.mun.ca/~yuri/Courses/MechanicalSystems/Turbomachinery.pdf {{Webarchive|url=https://web.archive.org/web/20180219004053/http://www.engr.mun.ca/~yuri/Courses/MechanicalSystems/Turbomachinery.pdf |date=2018-02-19 }}</ref>}}
{{term|term='''[[Turbulence]]'''}}{{defn|defn=In [[fluid dynamics]], turbulence or '''turbulent flow''' is fluid motion characterized by [[Chaos theory|chaotic]] changes in [[pressure]] and [[flow velocity]].  It is in contrast to a [[laminar flow]], which occurs when a fluid flows in parallel layers, with no disruption between those layers.<ref name=Batchelor>{{cite book | last=Batchelor | first=G. | title=Introduction to Fluid Mechanics | year=2000}}</ref>}}

{{glossary end}}{{Glossary of engineering: M - Z ToC}}

== U ==
{{glossary}}

{{term|term='''[[Ultimate tensile strength]]'''}}{{defn|defn='''Ultimate tensile strength''' ('''UTS'''), often shortened to '''tensile strength''' ('''TS'''), '''ultimate strength''', or '''Ftu''' within equations,<ref name="stressebook.com" /><ref name="Degarmo 2003 31"/><ref name="Smith 2006 223"/> is the capacity of a material or structure to withstand loads tending to elongate, as opposed to [[compressive strength]], which withstands loads tending to reduce size. In other words, tensile strength resists [[tension (physics)|tension]] (being pulled apart), whereas compressive strength resists [[compression (physics)|compression]] (being pushed together). Ultimate tensile strength is measured by the maximum [[stress (mechanics)|stress]] that a material can withstand while being stretched or pulled before breaking. In the study of [[strength of materials]], tensile strength, compressive strength, and [[shear strength]] can be analyzed independently.}}
{{term|term='''[[Uncertainty principle]]'''}}{{defn|defn=In [[quantum mechanics]], the '''uncertainty principle''' (also known as '''Heisenberg's uncertainty principle''') is any of a variety of [[Inequality (mathematics)|mathematical inequalities]]<ref name=Sen2014>{{Cite journal |last1 = Sen | first1 = D. | title = The Uncertainty relations in quantum mechanics | url = http://www.currentscience.ac.in/Volumes/107/02/0203.pdf | journal = Current Science | volume = 107| issue = 2| year = 2014| pages = 203–218 }}</ref> asserting a fundamental limit to the precision with which certain pairs of physical properties of a [[particle]], known as [[Complementarity (physics)|complementary variables]], such as [[Position (vector)|position]] ''x'' and [[momentum]] ''p'', can be known.}}
{{term|term='''[[Unicode]]'''}}{{defn|defn=A standard for the consistent encoding of textual characters.}}
{{term|term='''[[Unit vector]]'''}}{{defn|defn=In [[mathematics]], a '''unit vector''' in a [[normed vector space]] is a [[Vector space|vector]] (often a [[vector (geometry)|spatial vector]]) of [[Norm (mathematics)|length]] 1. A unit vector is often denoted by a lowercase letter with a [[circumflex]], or "hat": <math alt= i-hat>{\hat{\imath}}</math> (pronounced "i-hat"). The term [[direction vector]] is used to describe a unit vector being used to represent spatial direction, and such quantities are commonly denoted as '''d'''. .}}
{{term|term='''[[Unsaturated compound]]'''}}{{defn|defn=.}}
{{term|term='''[[Upthrust]]'''}}{{defn|defn=Buoyancy, or upthrust, is an upward [[force]] exerted by a [[fluid]] that opposes the [[weight]] of a partially or fully immersed object. In a column of fluid, pressure increases with depth as a result of the weight of the overlying fluid. Thus the pressure at the bottom of a column of fluid is greater than at the top of the column. Similarly, the pressure at the bottom of an object submerged in a fluid is greater than at the top of the object. The pressure difference results in a net upward force on the object. The magnitude of the force is proportional to the pressure difference, and (as explained by [[Archimedes' principle]]) is equivalent to the weight of the fluid that would otherwise occupy the submerged volume of the object, i.e. the [[Displacement (fluid)|displaced]] fluid.}}
{{term|term='''[[Utility frequency]]'''}}{{defn|defn=The utility frequency, (power) line frequency ([[American English]]) or mains frequency ([[British English]]) is the nominal [[frequency]] of the oscillations of [[alternating current]] (AC) in a [[wide area synchronous grid]] transmitted from a [[power station]] to the [[end-user]]. In large parts of the world this is 50&nbsp;[[hertz|Hz]], although in the [[Americas]] and parts of [[Asia]] it is typically 60&nbsp;Hz. Current usage by country or region is given in the list of [[mains electricity by country]].}}
{{glossary end}}

== V ==
{{glossary}}
{{term|term='''[[Vacuole]]'''}}{{defn|defn=Is a [[Biological membrane|membrane]]-bound [[organelle]] which is present in [[plant cell|plant]] and [[fungi|fungal]] [[Cell (biology)|cells]] and some [[protist]], [[animal]]<ref>{{cite book | last = Venes | first = Donald | name-list-style = vanc | date = 2001 | title = Taber's Cyclopedic Medical Dictionary | url = https://archive.org/details/taberscyclopedic19vene | url-access = registration | edition = Twentieth | publisher = F.A. Davis Company | location = Philadelphia | page = 2287 | isbn = 0-9762548-3-2 }}</ref> and [[bacteria]]l cells.<ref name=bacteria>{{cite book |volume =1|pages=295–298 |year=2006 | first = Heide N. | last = Schulz-Vogt | name-list-style = vanc |title=Inclusions in Prokaryotes |doi=10.1007/3-540-33774-1_10|series=Microbiology Monographs|isbn=978-3-540-26205-3|chapter=Vacuoles }}</ref> Vacuoles are essentially enclosed compartments which are filled with water containing inorganic and organic molecules including [[enzymes]] in [[solutes|solution]], though in certain cases they may contain solids which have been engulfed. Vacuoles are formed by the fusion of multiple membrane [[vesicle (biology)|vesicles]] and are effectively just larger forms of these.<ref>{{cite book | first1 = Robert J | last1 = Brooker | first2 = Eric P | last2 = Widmaier | first3 = Linda E | last3 = Graham | first4 = Peter D | last4 = Stiling | name-list-style = vanc | date = 2007 | title = Biology | edition = First | publisher = McGraw-Hill | location = New York | page = [https://archive.org/details/biology2008broo/page/79 79] | isbn = 978-0-07-326807-1 | url = https://archive.org/details/biology2008broo/page/79 }}</ref> The organelle has no basic shape or size; its structure varies according to the requirements of the cell.}}
{{term|term='''[[Vacuum]]'''}}{{defn|defn=An absence of mass in a volume.}}
{{term|term='''[[Valence (chemistry)|Valence]]'''}}{{defn|defn=In [[chemistry]], the '''valence''' or '''valency''' of an [[chemical element|element]] is a measure of its combining power with other atoms when it forms [[chemical compound]]s or [[molecule]]s. The concept of  valence developed in the second half of the 19th century and helped successfully explain the molecular structure of inorganic and organic compounds.<ref name = "Partington">{{cite book |last=Partington |first=James Riddick |author-link= J.R. Partington |year=1921 |title=A text-book of inorganic chemistry for university students |url=https://archive.org/details/textbookofinorga00partuoft |edition=1st |ol=7221486M }}</ref> 
The quest for the underlying causes of valence led to the modern theories of chemical bonding, including the [[cubical atom]] (1902), [[Lewis structure]]s (1916), [[valence bond theory]] (1927), [[molecular orbital]]s (1928), [[VSEPR theory|valence shell electron pair repulsion theory]] (1958), and all of the advanced methods of [[quantum chemistry]].}} 
{{term|term='''[[Valence band]]'''}}{{defn|defn=In [[solid-state physics]], the valence band and conduction band are the [[electronic band structure|bands]] closest to the [[Fermi level]] and thus determine the [[electrical conductivity]] of the solid. In non-metals, the valence band is the highest range of [[electron]] [[energy|energies]] in which electrons are normally present at [[absolute zero]] temperature, while the conduction band is the lowest range of vacant [[electronic state]]s. On a graph of the [[electronic band structure]] of a material, the valence band is located below the Fermi level, while the conduction band is located above it. The distinction between the valence and conduction bands is meaningless in metals, because conduction occurs in one or more partially filled bands that take on the properties of both the valence and conduction bands.}} 
{{term|term='''[[Valence bond theory]]'''}}{{defn|defn=In [[chemistry]], valence bond (VB) theory is one of the two basic theories, along with [[molecular orbital theory|molecular orbital (MO) theory]], that were developed to use the methods of [[quantum mechanics]] to explain [[chemical bond]]ing. It focuses on how the [[atomic orbital]]s of the dissociated atoms combine to give individual chemical bonds when a molecule is formed. In contrast, molecular orbital theory has orbitals that cover the whole molecule.<ref>{{cite book| last1 = Murrell| first1 = J. N.| last2 = Kettle| first2 = S. F. A.| last3 = Tedder| first3 = J. M.| title = The Chemical Bond| edition = 2nd| publisher = John Wiley & Sons| year = 1985| isbn = 0-471-90759-6| url-access = registration| url = https://archive.org/details/chemicalbond0000murr_e8r6}}</ref>}}
{{term|term='''[[Valence electron]]'''}}{{defn|defn=In [[chemistry]] and [[physics]], a valence electron is an outer shell [[electron]] that is associated with an [[atom]], and that can participate in the formation of a [[chemical bond]] if the outer shell is not closed; in a single [[covalent bond]], both atoms in the bond contribute one valence electron in order to form a [[shared pair]].}} 
{{term|term='''[[Valence shell]]'''}}{{defn|defn=The valence shell is the set of [[atomic orbital|orbital]]s which are energetically accessible for accepting electrons to form [[chemical bond]]s. For main group elements, the valence shell consists of the ns and np orbitals in the outermost [[electron shell]]. In the case of [[transition metal]]s (the (n-1)d orbitals), and [[lanthanide]]s and [[actinide]]s (the (n-2)f and (n-1)d orbitals), the orbitals involved can also be in an inner electron shell. Thus, the ''shell'' terminology is a [[misnomer]] as there is no correspondence between the valence shell and any particular electron shell in a given element. A scientifically correct term would be ''valence orbital'' to refer to the energetically accessible orbitals of an element.}} 
{{term|term='''[[Valve]]'''}}{{defn|defn=Is a device or [[Heart valve|natural object]] that regulates, directs or controls the flow of a fluid (gases, liquids, fluidized solids, or [[slurries]]) by opening, closing, or partially obstructing various passageways. Valves are technically [[Piping and plumbing fittings|fittings]], but are usually discussed as a separate category. In an open valve, fluid flows in a direction from higher pressure to lower pressure. The word is derived from the Latin ''valva'', the moving part of a door, in turn from ''volvere'', to turn, roll.}}  
{{term|term='''[[van der Waals equation]]'''}}{{defn|defn=In [[chemistry]] and [[thermodynamics]], the Van der Waals equation (or '''Van der Waals equation of state'''; named after Dutch physicist [[Johannes Diderik van der Waals]]) is an [[equation of state]] that generalizes the [[ideal gas law]] based on plausible reasons that [[real gas]]es do not act [[Idealization (science philosophy)|ideally]]. The ideal gas law treats gas [[molecule]]s as [[point particle]]s that interact with their containers but not each other, meaning they neither take up space nor change [[kinetic energy]] during [[collision]]s (i.e. all collisions are [[Elastic collision|perfectly elastic]]).<ref name=PhysicalChemistry>{{cite book | first1 = Robert J. | last1 = Silbey | first2 = Robert A. | last2 = Alberty | first3 = Moungi G. | last3 = Bawendi | title = Physical Chemistry | edition = 4th | year = 2004 | publisher = Wiley | isbn = 978-0471215042}}</ref> The ideal gas law states that [[volume]] (''V'') occupied by ''n'' [[Mole (unit)|moles]] of any gas has a [[pressure]] (''P'') at [[temperature]] (''T'') in [[kelvin]]s<!-- lower-case and pluralized – see Kelvin#Usage conventions --> given by the following relationship, where ''R'' is the [[gas constant]]:
:<math>PV=nRT</math>

To account for [[Molecular volume|the volume]] that a real gas molecule takes up, the Van der Waals equation replaces ''V'' in the ideal gas law with <math>(V_m-b)</math>, where ''V<sub>m</sub>'' is the [[molar volume]] of the gas and ''b'' is the volume that is occupied by one mole of the molecules. This leads to:<ref name=PhysicalChemistry />

:<math>P(V_m - b)=R T</math>

The second modification made to the ideal gas law accounts for the fact that gas molecules do in fact interact with each other (they usually experience attraction at low pressures and repulsion at high pressures) and that real gases therefore show different compressibility than ideal gases. Van der Waals provided for [[intermolecular interaction]] by adding to the observed pressure ''P'' in the equation of state a term <math>a /V_m^2</math>, where ''a'' is a constant whose value depends on the gas. The '''Van der Waals equation''' is therefore written as:<ref name=PhysicalChemistry />

:<math>\left(P+a\frac1{V_m^2}\right)(V_m-b)=R T</math>
and, for ''n'' moles of gas, can also be written as the equation below:

:<math>\left(P+a \frac{n^2}{V^2}\right)(V-n b)=n R T</math>

where ''V<sub>m</sub>'' is the molar volume of the gas, ''R'' is the universal gas constant, ''T'' is temperature, ''P'' is pressure, and ''V'' is volume. When the molar volume ''V<sub>m</sub>'' is large, ''b'' becomes negligible in comparison with ''V<sub>m</sub>'', ''a/V<sub>m</sub><sup>2</sup>'' becomes negligible with respect to ''P'', and the Van der Waals equation reduces to the ideal gas law, ''PV<sub>m</sub>=RT''.<ref name=PhysicalChemistry />

It is available via its traditional derivation (a mechanical equation of state), or via a derivation based in [[statistical thermodynamics]], the latter of which provides the [[partition function (statistical mechanics)|partition function]] of the system and allows thermodynamic functions to be specified. It successfully approximates the behavior of real [[fluid]]s above their [[critical temperature]]s and is qualitatively reasonable for their [[liquid]] and low-pressure [[gas]]eous states at low temperatures. However, near the [[phase transition]]s between gas and liquid, in the range of ''p'', ''V'', and ''T'' where the liquid phase and the gas phase are in [[Thermodynamic equilibrium|equilibrium]], the Van der Waals equation fails to accurately model observed experimental behaviour, in particular that ''p'' is a constant function of ''V'' at given temperatures. As such, the Van der Waals model is not useful only for calculations intended to predict real behavior in regions near the [[Critical point (thermodynamics)|critical point]]. Corrections to address these predictive deficiencies have since been made, such as the [[#Maxwell equal area rule|equal area rule]] or the [[principle of corresponding states]].}} 
{{term|term='''[[van der Waals force]]'''}}{{defn|defn=In [[molecular physics]], the Van der Waals force, named after Dutch physicist [[Johannes Diderik van der Waals]], is a distance-dependent interaction between atoms or molecules. Unlike [[ionic bond|ionic]] or [[covalent bonds]], these attractions do not result from a chemical electronic bond; they are comparatively weak and therefore more susceptible to disturbance. The Van der Waals force quickly vanishes at longer distances between interacting molecules.}} 
{{term|term='''[[van 't Hoff equation]]'''}}{{defn|defn=Relates the change in the [[equilibrium constant]], {{math|''K''<sub>eq</sub>}}, of a chemical reaction to the change in [[temperature]], ''T'', given the [[Standard enthalpy of reaction|standard enthalpy change]], {{math|Δ<sub>r</sub>''H''<sup>⊖</sup>}}, for the process. It was proposed by Dutch chemist [[Jacobus Henricus van 't Hoff]] in 1884 in his book ''Études de dynamique chimique'' (''Studies in Dynamic Chemistry'').<ref>[http://nobelprize.org/nobel_prizes/chemistry/laureates/1901/hoff-bio.html Biography on Nobel prize website]. Nobelprize.org (1 March 1911). Retrieved on 2013-11-08.</ref>

The Van 't Hoff equation has been widely utilized to explore the changes in [[state functions]] in a [[thermodynamic system]]. The '''Van&nbsp;'t Hoff plot''', which is derived from this equation, is especially effective in estimating the change in [[enthalpy]] and [[entropy]] of a [[chemical reaction]].}} 
{{term|term='''[[van 't Hoff factor]]'''}}{{defn|defn=Is a measure of the effect of a solute on [[colligative properties]] such as [[osmotic pressure]], relative lowering in [[vapor pressure]], [[boiling-point elevation]] and [[freezing-point depression]]. The [[Van 't Hoff factor]] is the ratio between the actual concentration of particles produced when the substance is dissolved and the [[concentration]] of a substance as calculated from its mass. For most non-[[electrolyte]]s dissolved in water, the Van&nbsp;'t Hoff factor is essentially 1. For most [[ionic compound]]s dissolved in water, the Van&nbsp;'t Hoff factor is equal to the number of discrete ions in a [[formula unit]] of the substance. This is true for [[ideal solution]]s only, as occasionally [[ion pair]]ing occurs in solution. At a given instant a small percentage of the ions are paired and count as a single particle. Ion pairing occurs to some extent in all electrolyte solutions. This causes the measured Van&nbsp;'t Hoff factor to be less than that predicted in an ideal solution. The deviation for the Van&nbsp;'t Hoff factor tends to be greatest where the ions have multiple charges.}} 
{{term|term='''[[Variable capacitor]]'''}}{{defn|defn=Is a [[capacitor]] whose capacitance may be intentionally and repeatedly changed mechanically or electronically.  Variable capacitors are often used in [[LC circuit|L/C circuits]] to set the resonance frequency, e.g. to tune a radio (therefore it is sometimes called a '''tuning capacitor''' or '''tuning condenser'''), or as a variable [[Reactance (electronics)|reactance]], e.g. for [[impedance matching]] in [[antenna tuner]]s.}} 
{{term|term='''[[Variable resistor]]'''}}{{defn|defn=.}} 
{{term|term='''[[Vector space]]'''}}{{defn|defn=A vector space (also called a '''linear space''') is a [[set (mathematics)|set]] of objects called [[Vector (mathematics and physics)|''vectors'']], which may be [[Vector addition|added]] together and [[Scalar multiplication|multiplied]] ("scaled") by numbers, called ''[[scalar (mathematics)|scalars]]''. Scalars are often taken to be [[real number]]s, but there are also vector spaces with scalar multiplication by [[complex number]]s, [[rational number]]s, or generally any [[field (mathematics)|field]]. The operations of vector addition and scalar multiplication must satisfy certain requirements, called vector ''[[axiom]]s'' . To specify that the scalars are real or complex numbers, the terms '''real vector space''' and '''complex vector space''' are often used.}} 
{{term|term='''[[Venturi effect]]'''}}{{defn|defn=Is the reduction in [[fluid pressure]] that results when a fluid flows through a constricted section (or choke) of a pipe. The Venturi effect is named after its discoverer, the 18th century Italian [[physicist]], [[Giovanni Battista Venturi]].}} 
{{term|term='''[[Vibration]]'''}}{{defn|defn=Is a mechanical phenomenon whereby [[oscillation]]s occur about an [[equilibrium point]]. The word comes from Latin ''vibrationem'' ("shaking, brandishing"). The oscillations may be [[periodic function|periodic]], such as the motion of a pendulum—or [[random]], such as the movement of a tire on a gravel road.

Vibration can be desirable: for example, the motion of a [[tuning fork]], the [[Reed (music)|reed]] in a [[woodwind instrument]] or [[harmonica]], a [[mobile phone]], or the cone of a [[loudspeaker]].

In many cases, however, vibration is undesirable, wasting [[energy]] and creating unwanted [[sound]]. For example, the vibrational motions of [[engine]]s, [[electric motor]]s, or any [[Machine|mechanical device]] in operation are typically unwanted. Such vibrations could be caused by [[Engine balance|imbalances]] in the rotating parts, uneven [[friction]], or the meshing of [[gear]] teeth. Careful designs usually minimize unwanted vibrations.}}
{{term|term='''Virtual leak'''}}{{defn|defn=Traces of gas trapped in cavities within a vacuum chamber, slowly dissipating out in the main chamber, thus appearing like a leak from the outside.}} 
{{term|term='''[[Viscoelasticity]]'''}}{{defn|defn=In [[materials science]] and [[continuum mechanics]], viscoelasticity is the property of [[materials]] that exhibit both [[Viscosity|viscous]] and [[Elasticity (physics)|elastic]] characteristics when undergoing [[deformation (engineering)|deformation]]. Viscous materials, like water, resist [[shear flow]] and [[Strain (materials science)|strain]] linearly with time when a [[Stress (physics)|stress]] is applied. Elastic materials strain when stretched and immediately return to their original state once the stress is removed.

Viscoelastic materials have elements of both of these properties and, as such, exhibit time-dependent strain. Whereas elasticity is usually the result of [[chemical bond|bond]] stretching along [[crystallographic plane]]s in an ordered solid, viscosity is the result of the diffusion of atoms or molecules inside an [[amorphous]] material.<ref name=Meyers>Meyers and Chawla (1999): "Mechanical Behavior of Materials", 98-103.</ref>}} 
{{term|term='''[[Viscosity]]'''}}{{defn|defn=The '''viscosity''' of a [[fluid]] is the measure of its [[drag (physics)|resistance]] to gradual deformation by [[shear stress]] or [[tensile stress]].<ref>{{cite web|url=http://www.merriam-webster.com/dictionary/viscosity|title=viscosity|website=Merriam-Webster Dictionary|date=22 May 2023 }}</ref> For liquids, it corresponds to the informal concept of "thickness": for example, [[honey]] has a higher viscosity than [[water]].<ref>{{cite book| last = Symon| first = Keith| title = Mechanics| edition = 3rd| publisher = Addison-Wesley| date = 1971| isbn = 978-0-201-07392-8}}</ref>}} 
{{term|term='''[[Volt-ampere]]'''}}{{defn|defn=(VA), is the unit used for the [[apparent power]] in an [[electrical circuit]]. The apparent power equals the product of [[root-mean-square]] (RMS) [[voltage]] and RMS [[electrical current|current]].<ref>Ciletti, M. D., Irwin, J. D., Kraus, A. D., Balabanian, N., Bickard, T. A., and Chan, S. P. (1993). Linear circuit analysis. In ''Electrical Engineering Handbook,'' edited by R. C. Dorf. Boca Raton: CRC Press. (pp.82–87)</ref> In [[direct current]] (DC) circuits, this product is equal to the [[real power]] (active power)<ref>''IEEE 100 : the authoritative dictionary of IEEE standards terms.-7th ed.'' {{ISBN|0-7381-2601-2}}, page 23</ref> in [[watt]]s. Volt-amperes are useful only in the context of [[alternating current]] (AC) circuits. The volt-ampere is dimensionally equivalent to the [[watt]] (in [[SI units]], 1 VA = 1 N m A<sup>−1</sup> s <sup>−1</sup> A = 1 N m s <sup>−1</sup> = 1 J s <sup>−1</sup> = 1 W). VA rating is most useful in rating wires and switches (and other power handling equipment) for inductive loads.}} 
{{term|term='''[[Volt-ampere reactive]]'''}}{{defn|defn=In electric power [[Electric power transmission|transmission]] and [[Electric power distribution|distribution]], volt-ampere reactive (var) is a unit of measurement of [[AC power#Active, reactive, and apparent power|reactive power]]. Reactive power exists in an AC circuit when the current and voltage are not in phase. The term ''var'' was proposed by the Romanian [[electrical engineer]] [[Constantin Budeanu]] and introduced in 1930 by the [[International Electrotechnical Commission|IEC]] in [[Stockholm]], which has adopted it as the unit for [[electrical reactance|reactive]] power.

Special instruments called ''varmeters'' are available to measure the reactive power in a circuit.<ref name=":0b">{{Cite book|title=Electrical Machines, Drives and Power Systems|last=Wildi|first=Theodore|publisher=Pearson|year=2002|isbn=978-0-13-093083-5|pages=137}}</ref>

The unit "var" is allowed by the  [[International System of Units]] (SI) even though the unit var is representative of a form of power.<ref>{{Cite web |url=https://www.bipm.org/en/publications/si-brochure/section2-2-2.html |title=SI Brochure, 8th ed. |access-date=2021-10-02 |archive-date=2019-03-21 |archive-url=https://web.archive.org/web/20190321011225/https://www.bipm.org/en/publications/si-brochure/section2-2-2.html |url-status=dead }}</ref> SI allows one to specify units to indicate ''common sense physical considerations''.  Per EU [[directive 80/181/EEC]] (the "metric directive"), the correct symbol is lower-case "var",<ref>[http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:1980:039:0040:0050:EN:PDF#page=6 Council Directive on units of measurements 80/181/EEC] Chapter 1.2.3., p. 6: "Special names for the unit of power: the name volt–ampere (symbol ‘VA’) when it is used to express the apparent power of alternating electric current, and var (symbol ‘var’) when it is used to express reactive electric power."</ref> although the spellings "Var" and "VAr" are commonly seen, and "VAR" is widely used throughout the power industry.}} 
{{term|term='''[[Volta potential]]'''}}{{defn|defn=The '''Volta potential''' (also called '''Volta potential difference''', '''contact potential difference''', '''outer potential difference''', Δψ, or "delta psi") in [[electrochemistry]], is the [[electrostatic potential]] difference between two metals (or one metal and one [[electrolyte]]) that are in contact and are in thermodynamic equilibrium. Specifically, it is the potential difference between a point close to the surface of the first metal,  and a point close to the surface of the second metal (or [[electrolyte]]).<ref>[http://goldbook.iupac.org/C01293.html IUPAC Gold Book, definition of contact (Volta) potential difference.]</ref>}} 
{{term|term='''[[Voltage]]'''}}{{defn|defn='''Voltage''', '''electric potential difference''', '''electric pressure ''' or '''electric tension''' is the difference in [[electric potential]] between two points. The difference in electric potential between two points (i.e., voltage) is defined as the [[Work (electrical)|work]] needed per [[Test charge|unit of charge]] against a static [[electric field]] to move a [[test charge]] between the two points. In the [[SI unit|International System of Units]], the [[SI derived unit|derived unit]] for voltage is named ''[[volt]]''.<ref name="volt">{{SIbrochure8th}}, p. 144</ref> In SI units,  work per unit charge is expressed as joules per coulomb, where 1 volt = 1 [[joule]] (of work) per 1 [[coulomb]] (of charge). The official SI definition for ''volt'' uses power and current, where 1 volt = 1 [[watt]] (of power) per 1 [[ampere]] (of current).<ref name="volt"/>}} 
{{term|term='''[[Volumetric flow rate]]'''}}{{defn|defn=Also known as '''volume flow rate''', '''rate of fluid flow''' or '''volume velocity''', is the volume of fluid which passes per unit time; usually represented by the symbol {{mvar|Q}} (sometimes {{mvar|V̇}}). The [[SI unit]] is m<sup>3</sup>/s ([[Cubic metre per second|cubic metres per second]]).}} 
{{term|term='''[[von Mises yield criterion]]'''}}{{defn|defn=The '''von Mises yield criterion''' (also known as the maximum distortion energy criterion<ref>{{cite news|title=Von Mises Criterion (Maximum Distortion Energy Criterion)|url=https://www.engineersedge.com/material_science/von_mises.htm|access-date=8 February 2018|publisher=Engineer's edge}}</ref>) suggests that [[yield (engineering)|yielding]] of a ductile material begins when the [[Cauchy stress tensor#Stress deviator tensor|second deviatoric stress invariant]] <math>J_2</math> reaches a critical value.<ref name="von Mises, R. 1913">von Mises, R. (1913). ''Mechanik der festen Körper im plastisch deformablen Zustand.'' Göttin. Nachr. Math. Phys., vol. 1, pp. 582–592.</ref> It is part of plasticity theory that applies best to [[ductile]] materials, such as some metals. Prior to yield, material response can be assumed to be of a nonlinear elastic, viscoelastic, or linear elastic behavior.

In [[materials science]] and [[engineering]] the von Mises yield criterion can also be formulated in terms of the '''von Mises stress''' or '''equivalent tensile stress''', <math>\sigma_v</math>. This is a scalar value of stress that can be computed from the [[Cauchy stress tensor]]. In this case, a material is said to start yielding when the von Mises stress reaches a value known as [[yield strength]], <math>\sigma_y</math>. The von Mises stress is used to predict yielding of materials under complex loading from the results of uniaxial tensile tests. The von Mises stress satisfies the property where two stress states with equal distortion energy have an equal von Mises stress.}} 
{{glossary end}}{{Glossary of engineering: M - Z ToC}}

== W ==
{{glossary}}

{{term|term='''[[Watt]]'''}}{{defn|defn=The SI unit of power, rate of doing work.}}  
{{term|term='''[[Wave]]'''}}{{defn|defn=Is a disturbance that transfers [[energy]] through [[matter]] or space, with little or no associated [[mass]] transport. Waves consist of [[oscillation]]s or [[vibration]]s of a physical [[Transmission medium|medium]] or a [[field (physics)|field]], around relatively fixed locations. From the perspective of mathematics, waves, as functions of time and space, are a class of [[signal]]s.<ref>Pragnan Chakravorty, "What Is a Signal? [Lecture Notes],"&nbsp;IEEE Signal Processing Magazine, vol. 35, no. 5, pp. 175-177, Sept. 2018.&nbsp;https://doi.org/10.1109/MSP.2018.2832195</ref>}} 
{{term|term='''[[Wavelength]]'''}}{{defn|defn=Is the '''spatial period''' of a periodic wave—the distance over which the wave's shape repeats.<ref name=hecht>
{{cite book
 |first=Eugene
 |last=Hecht
 |year=1987
 |title=Optics
 |edition=2nd
 |publisher=Addison Wesley
 |isbn=978-0-201-11609-0
 |pages=15–16
 }}</ref><ref name=Flowers>
{{cite book
 |title=An introduction to numerical methods in C++
 |chapter=§21.2 Periodic functions
 |page=473
 |chapter-url=https://books.google.com/books?id=weYj75E_t6MC&pg=RA1-PA473
 |author=Brian Hilton Flowers
 |isbn=978-0-19-850693-5
 |year=2000
 |edition=2nd
 |publisher = Cambridge University Press
 }}</ref> 
It is thus the [[multiplicative inverse|inverse]] of the [[spatial frequency]]. Wavelength is usually determined by considering the distance between consecutive corresponding points of the same [[phase (waves)|phase]], such as crests, troughs, or [[zero crossing]]s and is a characteristic of both traveling waves and [[standing wave]]s, as well as other spatial wave patterns.<ref name=Seaway>
{{cite book
 |title=Principles of physics
 |author1=Raymond A. Serway |author2=John W. Jewett |pages=404, 440
 |url=https://books.google.com/books?id=1DZz341Pp50C&pg=PA404
 |edition=4th
 |isbn=978-0-534-49143-7
 |publisher=Cengage Learning
 |year=2006 }}</ref><ref>
{{cite book
 | title=The surface physics of liquid crystals
 | author=A. A. Sonin
 | publisher=Taylor & Francis
 | year=1995
 | isbn=978-2-88124-995-2
 | page=17
}}</ref> 
Wavelength is commonly designated by the [[Greek letter]] ''[[lambda]]'' (λ). 
The term ''wavelength'' is also sometimes applied to [[modulation|modulated]] waves, and to the sinusoidal [[envelope (mathematics)|envelopes]] of modulated waves or waves formed by [[Interference (wave propagation)|interference]] of several sinusoids.<ref>
{{cite book
 | title = Electromagnetic Theory for Microwaves and Optoelectronics
 |author1=Keqian Zhang |author2=Dejie Li
 |name-list-style=amp | publisher = Springer 
 | year = 2007
 | isbn = 978-3-540-74295-1
 | page = 533
 | url = https://books.google.com/books?id=3Da7MvRZTlAC&q=wavelength+modulated-wave+envelope&pg=PA533
 }}</ref>' .}} 
{{term|term='''[[Wedge (mechanical device)|Wedge]]'''}}{{defn|defn=Is a [[triangle|triangular]] shaped tool, and is a portable [[inclined plane]], and one of the six classical [[simple machine]]s. It can be used to separate two objects or portions of an object, lift up an object, or hold an object in place. It functions by converting a [[force]] applied to its blunt end into forces perpendicular ([[Surface normal|normal]]) to its inclined surfaces. <!-- this link is broken <ref>{{Citation | title = Wedges and screws | url = http://em-ntserver.unl.edu/Negahban/em223/note16/note16.htm | access-date = 2009-07-29}}.</ref> --> The [[mechanical advantage]] of a wedge is given by the ratio of the length of its slope to its width.<ref name="bowser">{{Citation | last = Bowser | first = Edward Albert | title = An elementary treatise on analytic mechanics: with numerous examples | publisher = D. Van Nostrand Company | pages= 202–203 | year = 1920 | edition = 25th | url = https://books.google.com/books?id=mE4GAQAAIAAJ}}.</ref><ref name="CEST">''McGraw-Hill Concise Encyclopedia of Science & Technology'', Third Ed., Sybil P. Parker, ed., McGraw-Hill, Inc., 1992, p. 2041.</ref> Although a short wedge with a wide angle may do a job faster, it requires more force than a long wedge with a narrow angle.}} 
{{term|term='''[[Weighted arithmetic mean]]'''}}{{defn|defn=The '''weighted arithmetic mean''' is similar to an ordinary [[arithmetic mean]] (the most common type of [[average]]), except that instead of each of the data points contributing equally to the final average, some data points contribute more than others. The notion of weighted mean plays a role in [[descriptive statistics]] and also occurs in a more general form in several other areas of mathematics. If all the weights are equal, then the weighted mean is the same as the [[arithmetic mean]]. While weighted means generally behave in a similar fashion to arithmetic means, they do have a few counterintuitive properties, as captured for instance in [[Simpson's paradox]].}} 
{{term|term='''[[Wet-bulb temperature]]'''}}{{defn|defn=The temperature of a wetted thermometer with an air current across it. Used in psychrometry.}} 
{{term|term='''[[Wheel and axle]]'''}}{{defn|defn=Are one of six [[simple machine]]s identified by Renaissance scientists drawing from Greek texts on technology.<ref>Wheel and Axle, The World Book Encyclopedia, World Book Inc., 1998, pp. 280-281</ref> The wheel and axle consists of a [[wheel]] attached to a smaller [[axle]] so that these two parts rotate together in which a force is transferred from one to the other. A [[hinge]] or [[bearing (mechanical)|bearing]] supports the axle, allowing rotation. It can amplify force; a small force applied to the periphery of the large wheel can move a larger load attached to the axle.}} 
{{term|term='''[[Winsorized mean]]'''}}{{defn|defn=Is a [[winsorising|winsorized]] [[statistical]] [[measure of central tendency]], much like the [[mean]] and [[median]], and even more similar to the [[truncated mean]]. It involves the calculation of the mean after replacing given parts of a [[probability distribution]] or [[Sampling (statistics)|sample]] at the high and low end with the most extreme remaining values,<ref>[[Yadolah Dodge|Dodge, Y]] (2003) ''The Oxford Dictionary of Statistical Terms'', OUP. {{ISBN|0-19-920613-9}} (entry for "winsorized estimation")</ref> typically doing so for an equal amount of both extremes; often 10 to 25 percent of the ends are replaced. The winsorized mean can equivalently be expressed as a [[weighted average]] of the truncated mean and the quantiles at which it is limited, which corresponds to replacing parts with the corresponding quantiles.}} 
{{term|term='''[[Work hardening]]'''}}{{defn|defn=Also known as '''strain hardening''', is the [[strength of materials|strengthening]] of a metal or polymer by [[plastic deformation]]. This strengthening occurs because of [[dislocation]] movements and dislocation generation within the [[crystal structure]] of the material.<ref name="Degarmo 2003 60">{{harvnb|Degarmo|Black|Kohser|2003|p=60}}.</ref>}} 
{{glossary end}}

== X-Z ==
{{Anchor|X}}{{glossary}}
{{term|term='''[[Cartesian coordinate system|X-axis]]'''}}{{defn|defn=In algebraic geometry, the axis on a [[Graph of a function|graph]] that is usually drawn left to right and usually shows the range of values of an [[independent variable]].<ref>[https://en.wiktionary.org/wiki/x-axis Wiktionary]</ref>}}
{{anchor|Y}}{{term|term='''[[Cartesian coordinate system|Y-axis]]'''}}{{defn|defn=In algebraic geometry, the axis on a [[Graph of a function|graph]] that is usually drawn from bottom to top and usually shows the range of values of [[variable (mathematics)|variable]] dependent on one other variable, or the second of two [[independent variable]]s.<ref>[https://en.wiktionary.org/wiki/y-axis Wiktionary]</ref>}} 
{{term|term='''[[Yield (engineering)|Yield]]'''}}{{defn|defn=The point of maximum elastic deformation of a material; above yield the material is permanently deformed.}} 
{{term|term='''[[Young's modulus]]'''}}{{defn|defn=A measure of the stiffness of a material; the amount of force per unit area require to produce a unit strain.}} 
{{anchor|Z}}{{term|term='''[[Cartesian coordinate system|Z-axis]]'''}}{{defn|defn=In algebraic geometry, the axis on a [[Graph of a function|graph]] of at least three [[dimension]]s that is usually drawn vertically and usually shows the range of values of a [[variable (mathematics)|variable]] dependent on two other variables or the third independent variable.<ref>[https://en.wiktionary.org/wiki/z-axis Wiktionary]</ref>}}
{{term|term='''[[Zero defects]]'''}}{{defn|defn=A quality assurance philosophy that aims to reduce the need for inspection of components by improving their quality.}}
{{term|term='''[[Zero force member]]'''}}{{defn|defn=In the field of [[engineering mechanics]], a '''zero force member''' is a member (a single truss segment) in a [[truss]] which, given a specific [[structural load|load]], is at rest: neither in [[tension (mechanics)|tension]], nor in [[compression (physical)|compression]]. In a truss a zero force member is often found at pins (any connections within the truss) where no external load is applied and three or fewer truss members meet. Recognizing basic zero force members can be accomplished by analyzing the [[force]]s acting on an individual pin in a physical [[system]].

''NOTE: If the pin has an external force or [[Moment (physics)|moment]] applied to it, then all of the members attached to that pin are not zero force members UNLESS the external force acts in a manner that fulfills one of the rules below:''

* If two non-collinear members meet in an unloaded [[Joint (building)|joint]], both are zero-force members.
* If three members meet in an unloaded joint of which two are collinear, then the third member is a zero-force member.

'''Reasons for Zero-force members in a truss system'''
*These members contribute to the stability of the structure, by providing buckling prevention for long slender members under compressive forces
*These members can carry loads in the event that variations are introduced in the normal external loading configuration.}}
{{term|term='''[[Zeroth law of thermodynamics]]'''}}{{defn|defn=The equivalence principle applied to temperature; two systems in thermal equilibrium with a third are also in thermal equilibrium with each other.}}
{{glossary end}}{{Glossary of engineering: M - Z ToC}}

== See also ==
{{colbegin}}
*[[Engineering]]
*[[National Council of Examiners for Engineering and Surveying]]
*[[Fundamentals of Engineering Examination]]
*[[Principles and Practice of Engineering Examination]]
*[[Graduate Aptitude Test in Engineering]]
*[[Glossary of aerospace engineering]]
*[[Glossary of civil engineering]]
*[[Glossary of electrical and electronics engineering]]
*[[Glossary of mechanical engineering]]
*[[Glossary of structural engineering]]
*[[Glossary of architecture]]
*[[Glossary of areas of mathematics]]
*[[Glossary of artificial intelligence]]
*[[Glossary of astronomy]]
*[[Glossary of biology]]
*[[Glossary of calculus]]
*[[Glossary of chemistry terms|Glossary of chemistry]]
*[[Glossary of ecology]]
*[[Glossary of economics]]
*[[Glossary of physics]]
*[[Glossary of probability and statistics]]
*{{slink|List of established military terms|Engineering}}
{{colend}}

==Notes==
{{reflist|group=note}}
{{reflist|group=lower-alpha}}
{{notelist}}
{{reflist|group=lower-alpha}}
{{notelist}}
{{reflist|group=Note}}

==References==
{{Reflist}}
{{reflist|group=p}}

==Sources==
* {{cite book |first=Carl B. |last=Boyer |author-link=Carl Benjamin Boyer |title=A History of Mathematics |edition=Second |publisher=John Wiley & Sons, Inc. |year=1991 |isbn=978-0-471-54397-8 |url-access=registration |url=https://archive.org/details/historyofmathema00boye }}
*{{Citation | last1 = Degarmo | first1 = E. Paul | last2 = Black | first2 = J T. | last3 = Kohser | first3 = Ronald A. | title = Materials and Processes in Manufacturing | publisher = Wiley | year = 2003 | edition = 9th | isbn = 978-0-471-65653-1}}.
* {{cite book |title=The Oxford dictionary of Statistical Terms |last=Dodge |first=Y. |year=2003 |publisher=Oxford University Press |isbn=0-19-920613-9 |url-access=registration |url=https://archive.org/details/oxforddictionary0000unse }}
* {{cite book
|last=Holzner
|first=S.
|year=2006
|title=Physics for Dummies
|url=https://www.amazon.com/gp/reader/0764554336
|publisher=John Wiley & Sons
|quote=Physics is the study of your world and the world  and universe around you.
|isbn=978-0-470-61841-7
|bibcode=2005pfd..book.....H
}}
* {{cite book
|last=Maxwell
|first=J.C.
|author-link=James Clerk Maxwell
|year=1878
|title=Matter and Motion
|url=https://archive.org/details/matterandmotion03maxwgoog
|quote=matter and motion.
|publisher=D. Van Nostrand
|isbn=978-0-486-66895-6
}}
*{{Citation | last1 = Smith | first1 = William F. | last2 = Hashemi | first2 = Javad | title = Foundations of Materials Science and Engineering | edition = 4th | year = 2006 | publisher = McGraw-Hill | isbn = 978-0-07-295358-9 | postscript =.}}
* {{cite book
|last1=Young
|first1=H.D.
|last2=Freedman
|first2=R.A.
|year=2014
|edition=13th
|title=Sears and Zemansky's University Physics with Modern Physics Technology Update
|publisher=Pearson Education
|isbn=978-1-292-02063-1
|title-link=University Physics
}}

{{Engineering fields}}
{{Glossaries of science and engineering}}

{{DEFAULTSORT:Glossary of engineering: M-Z}}
[[Category:Engineering]]
[[Category:Engineering disciplines]]
[[Category:Glossaries of science|engineering]]
[[Category:Safety]]
[[Category:Glossaries of technology|Engineering]]
[[Category:Wikipedia glossaries using description lists]]