Mu

**Mu** can be:

- Mu, **Μ** or **μ**, a letter in the Greek alphabet.
μ is used as a symbol for:
    - The SI prefix _micro_, meaning a factor of 10<sup>-6</sup> (one millionth).
        - μ by itself is often used as the "unit" of strain, though in this context it retains its SI prefix meaning, which is interchangeable with "x 10<sup>-6</sup>" or "ppm" (parts per million).
        - μ by itself is an abbreviation for the unit micron. Both the term and the abbreviation should not be used. The preferred terms are µm and micrometre
    - In mathematics,
        - The arithmetic mean of a statistical population
        - The Möbius function
        - The least-fixed-point-operator
        - A degree of membership from a fuzzy set.
    - In chemistry,
        - The chemical potential
    - In physics,
        - The coefficient of friction
        - The mobility coefficient
        - The permeability (electromagnetism) coefficient
        - The muon, an elementary particle
        - The standard gravitational parameter
        - The magnetic dipole moment
        - The linear density
        - Viscosity
        - Reduced mass
    - µTorrent, a freeware BitTorrent client for Microsoft Windows written in C++.
    - μZiq, An alias of Mike Paradinas.

**In Asian languages**:
- Mù, (穆), a Chinese surname
- Mu (unit of area) (亩/畝), a Chinese unit of area
- Mu (kana), represented by the Japanese kana む or ム
- Mu (negative) (無), a Japanese word important in Zen koan practice

**Mu** may also refer to:
- Muonium's atomic symbol
- Mu-metal, an alloy used for screening magnetic fields
- Mu (lost continent), a mythical continent in the Pacific Ocean subsequently appearing in several books, films, and games
- Mu (rocket), a Japanese rocket
- Mu Dan, Chinese poet and translator
- Mu Online, an online role-playing game
- Mu La Flaga, a character from the anime _Mobile Suit Gundam SEED_
- Aries Mu, a character from the cartoon Saint Seiya
- Groupe Mu, an interdisciplinary Belgian group focusing on linguistics and rhetoric
- Lemuria, a hypothetical lost continent

**MU** may stand for:
- Mauritius' ISO 3166-1 alpha-2 country code
- China Eastern Airlines's IATA code
- Manchester United Football club
- The Mothers' Union, global Anglican women's organisation
- Monitor unit, a unit used in radiation therapy
- Centimorgan or "map unit", a unit of recombinant frequency in genetics
- Multiple unit, such as a rail diesel car
- MU puzzle, a puzzle in _Gödel, Escher, Bach_
- University of Mumbai, formerly called the University of Bombay
- Marquette University
- Marshall University
- Miami University, a public university in Oxford, Ohio
- Millersville University of Pennsylvania
- Miskatonic University
- University of Missouri, a public university in Columbia, Missouri
- Mahidol University, a University in Thailand
- Manipal University, a university in Karnataka, India
- MU (70's band), an early 1970s psychedelic group led by Merrell Fankhauser and Jeff Cotton
- MU (00's band), a 00's electro-punk group made up of producer Maurice Fulton and his wife Mutsumi Kanamori.
- Mirror Universe (Star Trek), fictional parallel universe in which the plots of several Star Trek television episodes take place
- Magic-User, a class type in D&D, HackMaster, and many fantasy RPGs
- Musician, an enlisted rating in the United States Navy
- Isuzu MU Wizard
- Micron Technology