em

noun

a unit for measuring the width of printed matter, equal to the height of the type size being used.

late 18th century: the letter M represented as a word, since it is approximately this width.

1. short for them.

   let 'em know who's boss

Middle English: originally a form of hem, dative and accusative third person plural pronoun in Middle English; now regarded as an abbreviation of them.

prefix

variant spelling of en-¹, en-² assimilated before b, p (as in emblazon, emplacement ).

1. (added to nouns) forming verbs meaning ‘put into or on’.

   engulf

   embed

2. (added to nouns and adjectives) forming verbs expressing conversion into the specified state as in encrust, ennoble, or (in combination with the suffix -en ) embolden, enliven.

   embolden

   encrust

3. (added to verbs) in; into; on.

   ensnare

from French, from Latin in- . See also in-², a commonly found by-form.

1. within; inside.

   empathy

   energy

   enthusiasm

from Greek.