Mu (letter)

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

Greek alphabet
Αα	Alpha	Νν	Nu
Ββ	Beta	Ξξ	Xi
Γγ	Gamma	Οο	Omicron
Δδ	Delta	Ππ	Pi
Εε	Epsilon	Ρρ	Rho
Ζζ	Zeta	Σσς	Sigma
Ηη	Eta	Ττ	Tau
Θθ	Theta	Υυ	Upsilon
Ιι	Iota	Φφ	Phi
Κκ	Kappa	Χχ	Chi
Λλ	Lambda	Ψψ	Psi
Μμ	Mu	Ωω	Omega
History
Archaic local variants
Ligatures (ϛ, ȣ, ϗ) Diacritics
Numerals ϛ (6) ϟ (90) ϡ (900)
In other languages
Bactrian Coptic Albanian
Scientific symbols
Book Category Commons view talk edit

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.

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 [mi]. In monotonic orthography, the ancient version is written with an acute accent instead of a circumflex: μύ.

Use as symbol

The lowercase letter mu (μ) is used as a special symbol in many academic fields. The uppercase mu is not used, since 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
• the airspeed relative to rotor tip speed (or rotor advance ratio) in rotorcraft^[2]
• as a unit measure of time called microseconds where a lower-case μ is read as 'microseconds' such 10μs=10e-6s

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

in Evolutionary Algorithm:

• 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

Meat Science

unit to express ionic strength, the total of all anions and cations in muscle tissue, or added through salts and phosphates

Pharmacology

In pharmacology:

• an important opiate receptor

Orbital mechanics

In 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"

Software

In application names:

• μTorrent, a BitTorrent client

Cameras

The Olympus Corporation manufactures a series of digital cameras called Olympus µ[mju:]^[3] (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.^[4]

Character Encodings

• Greek Mu / Coptic Mu

^[5]

• Mathematical Mu

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.

In Popular Culture

Gaming

In the online game RuneScape, entering this character once caused a bug that would force other nearby players to log out, which was abused to great effect by those in pvp areas. It has since been patched, and, like all bug abuse, is against the runescape terms of service.^[6]

See also

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

References