Editing Mu (letter) (section)

===Physics and engineering===
In [[classical physics]] and [[engineering]]:
* the [[friction#Coefficient of friction|coefficient of friction]]<ref>{{Cite book |last=Dante |first=Roberto C. |title=Handbook of friction materials and their applications |date=2016 |publisher=Woodhead Publishing |isbn=978-0-08-100619-1 |series=Woodhead Publishing in materials |location=Cambridge |pages=2 |quote=In the case of dry friction w(X) is the coefficient of friction μ, which is affected by temperature speed and other variables…}}</ref> (also used in aviation as braking coefficient (see [[Braking action]]))
* [[reduced mass]] in the [[two-body problem]]<ref>{{Cite book |last=Kulp |first=Christopher W. |title=Classical mechanics: a computational approach with examples using mathematica and Python |last2=Pagonis |first2=Vasilis |date=2021 |publisher=CRC Press |isbn=978-1-138-49528-9 |edition=1st |location=Boca Raton, FL |quote=The single mass ''μ'' is called the ''reduced mass'' of the two-body system and represents an effective inertial mass appearing in the two-body problem.}}</ref>
* [[Standard gravitational parameter]] in celestial mechanics<ref>{{Cite book |last=Dodd |first=Richard |title=Using SI units in astronomy |date=2012 |publisher=Cambridge University Press |isbn=978-0-521-76917-4 |location=Cambridge |pages=96 |quote=The standard gravitational parameter μ, is the product of the Newtonian gravitational constant G, and the mass of a given celestial body.}}</ref>
* [[linear density]], or mass per unit length, in strings and other one-dimensional objects<ref>{{Cite book |last=Walker |first=Jearl |title=Halliday & Resnick fundamentals of physics |last2=Resnick |first2=Robert |last3=Halliday |first3=David |date=2014 |publisher=Wiley |isbn=978-1-118-23376-4 |edition=10th |location=Hoboken, NJ |pages=452 |quote=We call this ratio the ''linear density μ'' of the striing.}}</ref>
* [[permeability (electromagnetism)|permeability]] in electromagnetism<ref>{{Cite book |last=Jiles |first=David |title=Introduction to magnetism and magnetic materials |date=2016 |publisher=CRC Press, Taylor & Francis Group |isbn=978-1-138-44149-1 |edition=Third |location=Boca Raton London New York |pages=42 |quote=We can now make a general statement for the permeability ''μ'' and susceptibility ''{{mvar|χ}}''}}</ref>
* the [[magnetic dipole moment]] of a [[Electric current|current]]-carrying [[Coil (electrical engineering)|coil]]
* [[Viscosity#Dynamic (shear) viscosity|dynamic viscosity]] in fluid mechanics
* the [[Amplifier|amplification]] factor or [[Gain (electronics)|voltage gain]] of a [[triode]] [[vacuum tube]]<ref>{{cite book |last=Ballou |first=Glen|title=Handbook for Sound Engineers: The New Audio Cyclopedia |publisher=Howard W. Sams Co. |year=1987 |edition=1 |page=250 |isbn=0-672-21983-2 |quote=''Amplification factor or voltage gain'' is the amount the signal at the control grid is increased in amplitude after passing through the tube, which is also referred to as the Greek letter μ (mu) or voltage gain (V<sub>g</sub>) of the tube.}}</ref>
* the [[electrical mobility]] of a charged particle
* the [[Slowed rotor#Theory|rotor advance ratio]], the ratio of aircraft [[airspeed]] to rotor-tip speed in [[rotorcraft]]<ref>"[http://rotorcraft.arc.nasa.gov/tutorial/Nomenclature.htm#mu Nomenclature]" ''NASA''</ref><ref>{{Cite web|url=http://dictionary.reference.com/browse/advance+ratio|title=Definition}}</ref><!--large download <ref>Oliver, Michael. "[http://dspace.mit.edu/bitstream/handle/1721.1/28910/60495046.pdf;jsessionid=4914214DD2723B08238E70B668D773DC?sequence=1 A parametric analysis of the start-up procedure and flight characteristiscs of a gliding autogyro]" page 43. ''[[Massachusetts Institute of Technology School of Engineering#Aeronautics and Astronautics|MIT Aero]]'', February 2005. Accessed: December 2013. Size: 15MB and 114 pages</ref> -->
* the [[pore water pressure]] in saturated soil

In [[particle physics]]:
* the elementary particles called the [[muon]] and antimuon
* the [[proton-to-electron mass ratio]]<ref>{{Cite journal |last=Thompson |first=Rodger I. |date=2017 |title=Fundamental constants as monitors of the universe |url=http://www.worldscientific.com/doi/abs/10.1142/9789813226609_0476 |journal=MG14 |language=en |publisher=WORLD SCIENTIFIC |pages=3657–3663 |doi=10.1142/9789813226609_0476 |isbn=978-981-322-659-3 |quote=There are now observational constraints on the time variation of the proton to electron mass ratio μ at the 10−7 level.|arxiv=1602.03192 }}</ref>

In [[thermodynamics]]:
* the [[chemical potential]] of a system or component of a system