(em) noun
1. The name of the thirteenth letter in the English alphabet, written M or m.
2. Printing The square of the body size of a type; especially, a pica em, about 1/6 of an inch, used as a standard unit of measurement: originally, the space occupied by the letter M in a font.

Var. of EN–¹, used before the labials b, p, and m, as in embody, empower, etc.

Assimilated var. of EN–².

(əm, m) pron. Colloq.
Them. [OE heom dative plural of he he]