Mu (letter)
Greek alphabet  



History  
Use in other languages  
Related topics  
Mu (/ˈm(j)uː/;^{[1]}^{[2]} uppercase Μ, lowercase μ; Ancient Greek μῦ [mŷː], Greek: μι or μυ—both [mi]) is the twelfth letter of the Greek alphabet, representing the voiced bilabial nasal IPA: [m]. In the system of Greek numerals it has a value of 40.^{[3]} Mu was derived from the Egyptian hieroglyphic symbol for water, which had been simplified by the Phoenicians and named after their word for water, to become 𐤌^{img} (mem). Letters that derive from mu include the Roman M and the Cyrillic М, though the lowercase resembles a small Latin U (u).
Names
Ancient Greek
In Greek, the name of the letter was written μῦ and pronounced [mŷː].
Modern Greek
In Modern Greek, the letter is spelled μι and pronounced [mi]. In polytonic orthography, it is written with an acute accent: μί.^{[4]}^{[5]}
Use as symbol
The lowercase letter mu (μ) is used as a special symbol in many academic fields. Uppercase mu is not used, because it appears identical to Latin M.
Prefix for units of measurement
"μ" is used as a unit prefix denoting a factor of 10^{−6} (one millionth), in this context, the symbol's name is "micro".
 Metric prefix
 International System of Units prefix, also known as "SI prefix"
 The micrometre with a symbol of "μm" can also be referred to as the nonSI term "micron".
Mathematics
"μ" is conventionally used to denote certain things; however, any Greek letter or other symbol may be used freely as a variable name.
 a measure in measure theory
 minimalization in computability theory and Recursion theory
 the integrating factor in ordinary differential equations
 the degree of membership in a fuzzy set
 the Möbius function in number theory
 the population mean or expected value in probability and statistics
 the Ramanujan–Soldner constant
Physics and engineering
In classical physics and engineering:
 the coefficient of friction (also used in aviation as braking coefficient (see Braking action))
 reduced mass in the twobody problem
 Standard gravitational parameter in celestial mechanics
 linear density, or mass per unit length, in strings and other onedimensional objects
 permeability in electromagnetism
 the magnetic dipole moment of a currentcarrying coil
 dynamic viscosity in fluid mechanics
 the amplification factor or voltage gain of a triode vacuum tube^{[6]}
 the electrical mobility of a charged particle
 the rotor advance ratio, the ratio of aircraft airspeed to rotortip speed in rotorcraft^{[7]}^{[8]}
 the pore water pressure in saturated soil
In particle physics:
 the elementary particles called the muon and antimuon
 the protontoelectron mass ratio
In thermodynamics:
 the chemical potential of a system or component of a system
Computer science
 μ, population size from which in each generation λ offspring will generate (the terms μ and λ originate from evolution strategy notation)
In type theory:
 Used to introduce a recursive data type. For example, is the type of lists with elements of type (a type variable): a sum of unit, representing nil, with a pair of a and another (represented by ). In this notation, is a binding form, where the variable () introduced by is bound within the following term () to the term itself. Via substitution and arithmetic, the type expands to , an infinite sum of everincreasing products of (that is, a is any tuple of values of type for any ). Another way to express the same type is .
Chemistry
In chemistry:
 the prefix given in IUPAC nomenclature for a bridging ligand
Biology
In biology:
 the mutation rate in population genetics
 A class of Immunoglobulin heavy chain that defines IgM type Antibodies
Pharmacology
In pharmacology:
 an important opiate receptor
Orbital mechanics
 Standard gravitational parameter of a celestial body, the product of the gravitational constant G and the mass M
 planetary discriminant, represents an experimental measure of the actual degree of cleanliness of the orbital zone, a criterion for defining a planet. The value of μ is calculated by dividing the mass of the candidate body by the total mass of the other objects that share its orbital zone.
Music
 Mu chord
 Electronic musician Mike Paradinas runs the label Planet Mu which utilizes the letter as its logo, and releases music under the pseudonym μZiq, pronounced "music"
 Used as the name of the school idol group μ's, pronounced "muse", consisting of nine singing idols in the anime Love Live! School Idol Project
 Official fandom name of Kpop group f(x), appearing as either MeU or 'μ'
 Hiphop artist Muonboy has taken inspiration from the particle for his stage name and his first EP named Mu uses the letter as its title.
Cameras
The Olympus Corporation manufactures a series of digital cameras called Olympus μ [mju:]^{[9]} (known as Olympus Stylus in North America).
Linguistics
In phonology:
In syntax:
 μP (mu phrase) can be used as the name for a functional projection.^{[10]}
In Celtic linguistics:
 /μ/ can represent an Old Irish nasalized labial fricative of uncertain articulation, the ancestor of the sound represented by Modern Irish mh.
Character encodings
^{[11]}
Preview  Μ  μ  µ  Ⲙ  ⲙ  

Unicode name  GREEK CAPITAL LETTER MU  GREEK SMALL LETTER MU  MICRO SIGN  COPTIC CAPITAL LETTER MI  COPTIC SMALL LETTER MI  
Encodings  decimal  hex  dec  hex  dec  hex  dec  hex  dec  hex 
Unicode  924  U+039C  956  U+03BC  181  U+00B5  11416  U+2C98  11417  U+2C99 
UTF8  206 156  CE 9C  206 188  CE BC  194 181  C2 B5  226 178 152  E2 B2 98  226 178 153  E2 B2 99 
Numeric character reference  Μ 
Μ 
μ 
μ 
µ 
µ 
Ⲙ 
Ⲙ 
ⲙ 
ⲙ 
Named character reference  Μ  μ  µ  
ISO/IEC 88591  181  B5  
ISO/IEC 88597  204  CC  236  EC  
Code page 437, 850  230  E6  230  E6  
Code page 737  139  8B  163  A3  
Code page 851, 869  183  B7  230  E6  
Code page 1253  204  CC  236  EC  
Roman8, Roman9  243  F3  243  F3  
TeX  \mu  \micro 
Preview  𝚳  𝛍  𝛭  𝜇  𝜧  𝝁  

Unicode name  MATHEMATICAL BOLD CAPITAL MU 
MATHEMATICAL BOLD SMALL MU 
MATHEMATICAL ITALIC CAPITAL MU 
MATHEMATICAL ITALIC SMALL MU 
MATHEMATICAL BOLD ITALIC CAPITAL MU 
MATHEMATICAL BOLD ITALIC SMALL MU  
Encodings  decimal  hex  dec  hex  dec  hex  dec  hex  dec  hex  dec  hex 
Unicode  120499  U+1D6B3  120525  U+1D6CD  120557  U+1D6ED  120583  U+1D707  120615  U+1D727  120641  U+1D741 
UTF8  240 157 154 179  F0 9D 9A B3  240 157 155 141  F0 9D 9B 8D  240 157 155 173  F0 9D 9B AD  240 157 156 135  F0 9D 9C 87  240 157 156 167  F0 9D 9C A7  240 157 157 129  F0 9D 9D 81 
UTF16  55349 57011  D835 DEB3  55349 57037  D835 DECD  55349 57069  D835 DEED  55349 57095  D835 DF07  55349 57127  D835 DF27  55349 57153  D835 DF41 
Numeric character reference  𝚳 
𝚳 
𝛍 
𝛍 
𝛭 
𝛭 
𝜇 
𝜇 
𝜧 
𝜧 
𝝁 
𝝁 
Preview  𝝡  𝝻  𝞛  𝞵  

Unicode name  MATHEMATICAL SANSSERIF BOLD CAPITAL MU 
MATHEMATICAL SANSSERIF BOLD SMALL MU 
MATHEMATICAL SANSSERIF BOLD ITALIC CAPITAL MU 
MATHEMATICAL SANSSERIF BOLD ITALIC SMALL MU  
Encodings  decimal  hex  dec  hex  dec  hex  dec  hex 
Unicode  120673  U+1D761  120699  U+1D77B  120731  U+1D79B  120757  U+1D7B5 
UTF8  240 157 157 161  F0 9D 9D A1  240 157 157 187  F0 9D 9D BB  240 157 158 155  F0 9D 9E 9B  240 157 158 181  F0 9D 9E B5 
UTF16  55349 57185  D835 DF61  55349 57211  D835 DF7B  55349 57243  D835 DF9B  55349 57269  D835 DFB5 
Numeric character reference  𝝡 
𝝡 
𝝻 
𝝻 
𝞛 
𝞛 
𝞵 
𝞵 
Image list for readers with font problems
Text is available under the CC BYSA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.