em-

1
Compare im-1.

em-

2
  1. variant of en-2 before b, m, p, ph: embolism, emphasis.
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British Dictionary definitions for em-

em-

prefix
  1. before b, m, and p, a variant of en- 1, en- 2
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for em-
1

from French assimilation of en- to following labial (see en- (1)). Also a prefix used to form verbs from adjectives and nouns.

2

representing Latin ex- assimilated to following -m- (see ex-).

Online Etymology Dictionary, © 2010 Douglas Harper

em- in Medicine

em-

pref.
  1. Variant ofen-
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.