mu

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
Obsolete letters
	Digamma		Qoppa
	San		Sampi
Other characters
	Stigma		Sho
	Heta
Greek diacritics

Mu (uppercase Μ, lowercase μ; 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 () 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 letter М.

Usage

Ancient Greek

The word Mu, pronounced /muː/ or /mjuː/ in English, is written μῦ in traditional Greek polytonic orthography. In Modern Greek the ancient version is sometimes written μύ.

Modern Greek

In Modern Greek, the name of the letter is spelled μι and is pronounced [mi].

About

The letter Mu appears in conjunction with alpha and omega to signify the "beginning, middle (meson) and end", a phrase found in an Orphic verse describing Zeus, and later adopted to describe both JHWH and Jesus.

In Aeschylus' Eumenides, the repeated moaning of the letter Mu is the sound made by the sleeping Furies as the ghost of Clytemnestra begins to invoke them. It again appears as an ominous mantra in a 10th-century Coptic papyrus, containing a Christian injunction against perjurers that invokes the angel Temeluchos.

Academia

The lower-case letter mu is used as a special symbol in many academic fields. The upper case Mu is not generally used in this way because it is normally indistinguishable from the Latin M.

• In mathematics:
  • the µ-roots of a complex number z = a + bi
  • the Möbius function in number theory
  • the integrating factor in ordinary differential equations
  • the population mean or expected value in probability and statistics
  • a measure in measure theory
  • minimalization in computability theory and Recursion theory
  • the learning rate as used in artificial neural networks
• In measurement:
  • the SI prefix micro-, which represents one millionth, or 10⁻⁶.
  • the micron, an old unit which corresponds to the micrometre (which is now denoted "µm")
• 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 of a triode vacuum tube
  • the electrical mobility of a charged particle
• In inorganic chemistry:
  • the prefix given in IUPAC nomenclature for a bridging ligand.
• In particle physics:
  • the elementary particles called the muon and antimuon
• In Pharmacology:
  • an important opiate receptor
• In thermodynamics:
  • the chemical potential of a system or component of a system.
• In orbital mechanics:
  • Standard gravitational parameter of a celestial body, the product of the gravitational constant G and the mass M.
• In music:
  • Mu major chord

Computing

In Unicode, the upper and lower case mu are encoded at U+039C and U+03BC respectively. In ISO 8859-7 they are encoded at CC_HEX and EC_HEX. The micro sign or micron is considered a distinct character from the Greek alphabet letter by Unicode for historical reasons (although it is a homoglyph) and is found at U+00B5 as well as position B5_HEX in ISO 8859-1, 3, 8, 9, 13 and 15, and thus in the corresponding Windows code pages Windows-1252 etc. ISO-8859-5 also has a character that looks somewhat like lower case mu at E6_HEX but this is actually supposed to be the Cyrillic small letter tse (ц).

When Alt-0181 or the DOS legacy Alt+230 or Alt+{any multiple of 256 added to 230 or to 0181 and including the leading zero} is typed into an editable field using the numeric keypad in Microsoft Windows, the µ symbol appears. Also if AltGr + M is pressed you get µ. In HTML code, the µ symbol is represented by "µ", "µ" and the entities "µ" and "μ".

Because µ is the abbreviation for the metric system prefix micro-, the symbol is used in many word plays about the field of micro-computing. For example, the symbol is used in the name and logo of the popular bittorrent client, µTorrent. Also, the microcontrollers are commomnly represented in schematics as µC. It is sometimes simply substituted with a u, the most likely looking ASCII glyph, eg. uTorrent.

Popular culture

• Mike Paradinas, a British electronic musician, uses the letter in his stage name μ-ziq (pronounced music), as well as in the name of his record label Planet µ, often written Planet Mu.

References

• Moralia, by Plutarch
• Ancient Christian Magic, by M. Meyer and R. Smith (ed.), Princeton University Press, ISBN 0-691-00458-7