- a plural of micron.
- Also called micrometer. the millionth part of a meter. Symbol: μ, mu
- Physical Chemistry. a colloidal particle whose diameter is between 0.2 and 10 microns.
- Physics. a very small unit of pressure, equal to that exerted by a column of mercury 1μ high.
Origin of micron
1880–85; < Greek mīkrón a little, noun use of neuter singular of mīkrós small; see -on1
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Examples from the Web for micra
Read off the number of divisions it occupies and express them as micra.The Elements of Bacteriological Technique
John William Henry Eyre
- a plural of micron
- a unit of length equal to 10 –6 metre. It is being replaced by the micrometre, the equivalent SI unit
C19: New Latin, from Greek mikros small
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 micra
"one millionth of a meter," 1892, coined 1880 in French from Greek mikron, neuter of mikros "small" (see mica).
Online Etymology Dictionary, © 2010 Douglas Harper
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
- See micrometer2.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.