M is used as the unit abbreviation for molarity.However, m is also used as an abbreviation for mile. m is the standard abbreviation for metre (or meter) in the International System of Units (SI).Unit prefix M (mega), meaning one million times, and m (milli) meaning one-thousandth.There is, however, scant evidence that the letter was later introduced in the early centuries A.D. The Roman numeral M represents the number 1000, though it was not used in Roman times.Styled letter M in the coat of arms of Miehikkälä In Washo, lower-case ⟨m⟩ represents a typical em sound, while upper-case ⟨M⟩ represents a voiceless em sound. In modern terminology, this is described as a syllabic consonant (IPA ). In English, the Oxford English Dictionary (first edition) says that ⟨m⟩ is sometimes a vowel, in words like spasm and in the suffix -ism. The letter ⟨m⟩ represents the bilabial nasal consonant sound in the orthography of Latin as well as in that of many modern languages, and also in the International Phonetic Alphabet. The Egyptian sign had the acrophonic value /n/, from the Egyptian word for "water", nt the adoption as the Semitic letter for /m/ was presumably also on acrophonic grounds, from the Semitic word for "water", *mā(y). Semitic Mem is most likely derived from a " Proto-Sinaitic" ( Bronze Age) adoption of the "water" ideogram in Egyptian writing. The letter M is derived from the Phoenician Mem, via the Greek Mu (Μ, μ). 4.2 Ancestors and siblings in other alphabets.4.1 Descendants and related characters in the Latin alphabet.