M

The letter M is the thirteenth letter in the Latin alphabet. Its name in English is em [ɛm].

History

The letter M derives its shape from the Phoenician Mem, via the Greek Mu (Μ, μ). Semitic Mem probably originally pictured water. It is speculated that Semitic people working in Egypt c. 2000 BC borrowed a hieroglyph for Water that was first used for an alveolar nasal (/n/, because of the Egyptian word for Water, "n-t". This same symbol became used for M in Semitic, because their word for water began with that sound.

Egyptian hieroglyph "N"

Proto-Semitic M

Phoenician M

Etruscan M

Greek Mu

The letter M represents the bilabial nasal consonant sound, IPA [m], in Classical languages as well as the modern languages. The Oxford English Dictionary (first edition) says that 'm' is sometimes a vowel in words like spasm and in the suffix -ism. In modern terminology, this would be described as a syllabic consonant — IPA [m̩].

Codes for computing

class="template-letter-box | In Unicode the capital M is codepoint U+004D and the lowercase m is U+006D.

The ASCII code for capital M is 77 and for lowercase m is 109; or in binary 01001101 and 01101101, correspondingly.

The EBCDIC code for capital M is 212 and for lowercase m is 148.

The numeric character references in HTML and XML are "M" and "m" for upper and lower case respectively.

Abbreviations for M in everyday use

In information systems, M is often used as the abbreviation for the male sex in personal data records.
In calendars, M is often an abbreviation for Monday or for the months March or May.
In Control Theory, M is the magnitude of the closed-loop frequency response.
In French, and some English works by French authors, M. is an abbreviation for Monsieur.
In clothing, M can mean "medium size". European clothing-size standard EN 13402 defines the size code M to refer to chest girths 94–102 cm for men's clothes and bust girths 90–98 cm for women's clothes. Manufacturers also use their own non-standard defining body measurements for this size code.
In engineering, M designates an ISO metric screw thread, as in "an M8 screw".
As an academic degree, M means magister or master.

Arts and popular culture

Comic books

M is a member of "Generation X", a team of younger mutants affiliated with and coached by some of the former "X-Men".
M is a Norwegian comic strip.

Games

M is the ESRB rating symbol for Mature.
M is the abbreviation for Mario, a Nintendo character. He wears a red hat which has a red capital "M" on it.
'M is the nickname of a certain glitch in the Pokémon video games, which takes the form of a wild pokémon..
A player's "M" in poker is a measure of the health of his chip stack.

Transportation

M is a New York City Subway line, the M train, which runs between Metropolitan Avenue in Queens, through Manhattan, to Bay Parkway in Brooklyn

Film

M is the codename of the head of MI6 in the James Bond books and films; see M (James Bond).
M is a German film from 1931 directed by Fritz Lang about a serial killer who preys on children; see M (1931 film). The film was remade in Hollywood in 1951; see M (1951 film).
M is a defunct rating in the MPAA rating system. It denoted films that MPAA classified as 'for Mature Audiences: Parental discretion advised.' It was used very briefly, from 1968 to 1969. It was followed by 'GP' in 1969, and by 'PG' in 1970.
M is a rating used by the Australian Office of Film and Literature Classification (Australia) denoting that the film may contain material that requires a semi-mature perspective, it imposes no restrictions on who may view it.
M is also the name of a now-defunct professional videocassette format developed by Matsushita and RCA.
The names of many heroines in Hitchcock movies start with the letter M (this applies to aliases, too, such as in Marnie).

Music

M is the assumed name of the artist Robin Scott, who performed the 1979 #1 hit song "Pop Muzik".
-M- is the artist name of the French singer Matthieu Chédid.
"M" is the pseudonym for a Jazz vocalist hired by Yoko Kanno (see M (singer))
M can be a reference to rapper Eminem
M is a song by Ayumi Hamasaki
M, a song by The Cure from their 1980 album Seventeen Seconds
M is the first letter of the name assumed by Mattew Miller for his music career, Matisyahu.
M People were a band popular in the 1990s.
A lower-case m placed after a note name indicates a minor chord (e.g., Em for an E minor chord).
M, a male Korean singer also known as Lee Min Woo

Business

M closely resembles the symbol of McDonald's, known as the Golden Arches.

Photography

In photography, most SLR cameras use M to signify manual mode, where the user sets both aperture and shutter speed.

Finance

In common references to currency, M or m denotes million or millions, such as $25M (twenty-five million dollars).
In traditional accounting practice, M designates thousand or thousands (from the Latin mille), and MM is used for million. Hence such traditional abbreviations as CPM for cost per thousand items of a retail good, or MCF for thousand cubic feet of (e.g.) natural gas.
In economics, M is usually used to represent imports.
Script capital M (Unicode 0x2133 ℳ) denotes the old German currency Goldmark.

Geographical abbreviations

In international licence plate codes, M stands for Malta.
As the first letter of a postal code:
- In Canada, M stands for the City of Toronto.
- In the United Kingdom, M stands for Manchester.
In radiocommunication, M is one of the ITU prefixes allocated to the United Kingdom.
M is an abbreviation for the Russian design bureau Myasishchev
In Denmark, the Copenhagen Metro is often abbreviated to M.

Grammar

In grammar, M is often the abbreviation for the masculine grammatical gender.

Military

M is the US military designation for "Model" in weapons, vehicles and other equipment, but not military aircraft. Started use in the early to mid 1930's. Prior usage was the word Model of with the year of adoption or standardization. The correct current usage is with the letter M and then the number assigned, e.g. M16 rifle, etc.
In war time, the letter M is often written on the forehead of casualties to alert medics that the patient has been given morphine.
In the NATO phonetic alphabet, M is "Mike".
The NATO M band ranges from 60 to 100 GHz.

Science, computing and industry

Astronomy

In astronomy, M is an abbreviation for "Messier" in designations for the Messier Deepsky Objects.
M stands for a reddish class of stars in the Morgan-Keenan system.
M stands for a June 16 through 30 discovery, in the provisional designation of a comet (e.g. C/1860 M1, the Great Comet of 1860) or asteroid (e.g. (4314) 1979 ML3).
M would stand for Mars, in the provisional designation of any ring or natural satellite discovered around it.

Biochemistry

In biochemistry, M is the symbol for methionine.

Chemistry

M is the symbol for the molarity of solutions.
m is the symbol for the sample mass of compounds.
m is also the symbol for the molality of the compound.

Colour

In the CMYK color model, M stands for the colour magenta.

Computing

M, when used as a binary prefix, means 2²⁰ = 1,048,576 (cf. M as a metric prefix below, and the prefix mebi: Mi).
M is another name for the computer programming language MUMPS.

Mathematics

m is used to denote slope in slope-intercept form. An M-set is the opposite of a set of uniqueness.
Script capital M (Unicode 0x2133 ℳ) denotes a matrix.
In the 1973 Handbook of Integer Sequences (a printed predecessor of the OEIS) sequences were numbered in lexicographic order prefixed by the letter M. Some older mathematical papers use these M numbers.

Measurement (SI system)

M (mega) is an SI prefix denoting 10⁶ = 1,000,000 (one million) (cf. M in computing above)
m (milli) is an SI prefix meaning 1/1000.
- m denotes metre (or meter), the SI base unit for length.
m is a widely used abbreviation for mile, as seen, for example, on road signs in the UK. In such instances, the metre is usually abbreviated as 'mtr' or similar to avoid confusion with miles.

Physics

Upper-case M represents a constant mass property of an object of matter.
Lower-case m represents a mass variable of matter in change.
M-theory is a proposed solution for problems in superstring theories.
Script capital M (Unicode 0x2133 ℳ) denotes a torque.
Upper-case M represents mutual inductance.

Printing

A capital M with a strikethrough (M) is used in the printing industry to denote one thousand, as in run quantity. For example, 4M is the equivalent of 4,000.

Automotive

M is the symbol for the high end performance BMW cars: M1, M3, M5, M6, Z3 M and the new Z4 M.

Medicine

In a medical prescription, M means misce (Latin for "mix").

Roman uses for M

In the Roman naming convention, M is the abbreviation for the praenomen Marcus, and M' stands for Manius.
In Roman numerals, M denotes one thousand. While the symbol had originally a different shape, it took on the shape of an M based on the association with Latin mille ("one thousand"). There are also separate Unicode characters for this number, 0x216F "Ⅿ" and 0x217F "ⅿ".
In antiquity, the letter M was considered a symbol of eccentricity, based on the Greek word μωρός ("stupid").

Theology

In theology and higher criticism, M is an abbreviation for "M Gospel".
In Christian symbolism, M is a symbol of the Trinity, because of its three vertical lines.