# Mu (letter)

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Look up or Μ in Wiktionary, the free dictionary.μ |

**Lua error in package.lua at line 80: module 'strict' not found.** **Mu** (uppercase **Μ**, lowercase **μ**; Ancient Greek μῦ [mŷː], Modern Greek μι or μυ [mi]) is the 12th letter of the Greek alphabet. In the system of Greek numerals it has a value of 40. Mu was derived from the Egyptian hieroglyphic symbol for water (𓈖), which had been simplified by the Phoenicians and named after their word for water, to become(mem). Letters that arose from mu include the Roman M and the Cyrillic М.

## Contents

## Names

### Ancient Greek

In Ancient Greek, the name of the letter was written μῦ and pronounced [mŷː].

### Modern Greek

In Modern Greek, the letter is spelled μι and pronounced [me]. In monotonic orthography, the ancient version is written with an acute accent instead of a circumflex: μύ.

## Use as symbol

The lowercase letter me (μ) is used as a special symbol in many academic fields. The uppercase mu is not used, because it is normally identical to Latin M.

### Measurement

- the SI prefix
*micro-*, which represents one millionth, or 10^{−6} - the micron, an old unit that corresponds to the micrometre (which is now denoted "µm")

### Mathematics

*This is not exhaustive, since any Greek letter may be used freely as a variable name.*

- a measure in measure theory
- minimalization in computability theory and Recursion theory
- the mean in the normal distribution
- the integrating factor in ordinary differential equations
- the learning rate in artificial neural networks
- the Möbius function in number theory
- the population mean or expected value in probability and statistics

### Physics and engineering

In classical physics and engineering:

- the coefficient of friction (also used in aviation as braking coefficient)
- reduced mass in the two-body problem
- linear density, or mass per unit length, in strings and other one-dimensional objects
- permeability in electromagnetism
- the magnetic dipole moment of a current-carrying coil
- dynamic viscosity in fluid mechanics
- the amplification factor or voltage gain of a triode vacuum tube
^{[1]} - the electrical mobility of a charged particle
- a.k.a. rotor advance ratio; the ratio of aircraft airspeed to rotor tip speed in rotorcraft
^{[2]}^{[3]}

In particle physics:

- the elementary particles called the muon and antimuon

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)

### Chemistry

In chemistry:

- the prefix given in IUPAC nomenclature for a bridging ligand

### 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 major chord
- Electronic musician Mike Paradinas runs the label Planet Mu which utilizes the letter as its logo, and releases music under the pseudonym µ-Ziq, pronounced "music"
- Idol group name of 9 singing teen girls in the anime Love Live! School Idol Project

### Software

In application names:

- μTorrent, a BitTorrent client

### Cameras

The Olympus Corporation manufactures a series of digital cameras called Olympus µ[mju:]^{[4]} (known as Olympus Stylus in North America)

### Linguistics

In phonology, it often stands for mora. In syntax, μP (mu phrase) can be used as the name for a functional projection.^{[5]}

## Character Encodings

- Greek Me / Coptic Mu
^{[6]}

Character | Μ | μ | µ | Ⲙ | ⲙ | |||||
---|---|---|---|---|---|---|---|---|---|---|

Unicode name |
GREEK CAPITAL LETTER ME | GREEK SMALL LETTER ME | MICRO SIGN | COPTIC CAPITAL LETTER ME | COPTIC SMALL LETTER ME | |||||

Encodings | decimal | hex | decimal | hex | decimal | hex | decimal | hex | decimal | hex |

Unicode | 924 | U+039C | 956 | U+03BC | 181 | U+00B5 | 11416 | U+2C98 | 11417 | U+2C99 |

UTF-8 | 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 | |||||||

DOS Greek | 139 | 8B | 163 | A3 | ||||||

DOS Greek-2 | 183 | B7 | 230 | E6 | ||||||

Windows 1253 | 204 | CC | 236 | EC | ||||||

TeX | \me |

- Mathematical Me

Character | 𝚳 | 𝛍 | 𝛭 | 𝜇 | 𝜧 | 𝝁 | ||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|

Unicode name |
MATHEMATICAL BOLD CAPITAL ME |
MATHEMATICAL BOLD SMALL ME |
MATHEMATICAL ITALIC CAPITAL ME |
MATHEMATICAL ITALIC SMALL ME |
MATHEMATICAL BOLD ITALIC CAPITAL ME |
MATHEMATICAL BOLD ITALIC SMALL ME |
||||||

Encodings | decimal | hex | decimal | hex | decimal | hex | decimal | hex | decimal | hex | decimal | hex |

Unicode | 120499 | U+1D6B3 | 120525 | U+1D6CD | 120557 | U+1D6ED | 120583 | U+1D707 | 120615 | U+1D727 | 120641 | U+1D741 |

UTF-8 | 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 |

UTF-16 | 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 |

Character | 𝝡 | 𝝻 | 𝞛 | 𝞵 | ||||
---|---|---|---|---|---|---|---|---|

Unicode name |
MATHEMATICAL SANS-SERIF BOLD CAPITAL ME |
MATHEMATICAL SANS-SERIF BOLD SMALL ME |
MATHEMATICAL SANS-SERIF BOLD ITALIC CAPITAL ME |
MATHEMATICAL SANS-SERIF BOLD ITALIC SMALL ME |
||||

Encodings | decimal | hex | decimal | hex | decimal | hex | decimal | hex |

Unicode | 120673 | U+1D761 | 120699 | U+1D77B | 120731 | U+1D79B | 120757 | U+1D7B5 |

UTF-8 | 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 |

UTF-16 | 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 |

These characters are used only as mathematical symbols. Stylized Greek text should be encoded using the normal Greek letters, with markup and formatting to indicate text style.

## See also

- Greek letters used in mathematics, science, and engineering
- Л, л - El (Cyrillic)
- Fraser alphabet#Consonants

## References

- ↑
**Lua error in package.lua at line 80: module 'strict' not found.** - ↑ "Nomenclature"
*NASA* - ↑ Definition
- ↑ Olympus History : µ[mju:] (Stylus) Series
- ↑
**Lua error in package.lua at line 80: module 'strict' not found.** - ↑ Unicode Code Charts: Greek and Coptic (Range: 0370-03FF)