What do a.m. and p.m. stand for?


[em] /ɛm/
noun, plural ems.
the letter M, m.
Also called mut, mutton. Printing.
  1. the square of any size of type used as the unit of measurement for matter printed in that type size.
  2. (originally) the portion of a line of type occupied by the letter M in type of the same size.
Printing. having the area of an em quad or the length of an em dash.
Origin of em
1860-65 Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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British Dictionary definitions for em's


noun (printing)
Also called mutton, mut. the square of a body of any size of type, used as a unit of measurement
Also called pica em, pica. a unit of measurement used in printing, equal to one sixth of an inch
Word Origin
C19: from the name of the letter M
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
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em's in Medicine

EM abbr.
electron microscope

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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Related Abbreviations for em's


  1. electromagnetic
  2. electron microscope
  3. enlisted man
The American Heritage® Abbreviations Dictionary, Third Edition
Copyright © 2005 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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