M is the thirteenth letter of the English Alphabet, and a labial articulation, formed by a compression of the lips. It is called a semi-vowel, as the articulation or compression of the lips is accompanied with a humming sound through the nose, which constitutes a difference between this letter and b. Its sound is uniform; as in man, time, rim.

M is a numeral letter, and among the ancients stood for a thousand; a use which is retained by the moderns. With a dash or stroke over it, it stands for a thousand times a thousand, or a million.

As an abbreviation, m stands for Marcus, Martius, Manlius or Mutius.

A.M. or M.A. stands for artium magister, master of arts; m D. for medicinoe doctor, doctor of medicine; adjective M. for anno mundi, the year of the world; MS, for manuscript; MSS, for manuscripts.

In astronomical tables, m stands for meridian, meridional, or mid-day.

In medical prescriptions, m stands for maniple, or handful, or misce, mix, or mixtura, a mixture.

In the late British Pharmacopaeias it signifies mensura, by measure.

In law, m is a brand or stigma impressed on one convicted of manslaughter, and admitted to the benefit of clergy.