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micra

[mahy-kruh] /ˈmaɪ krə/
noun
1.
a plural of micron.

micron

[mahy-kron] /ˈmaɪ krɒn/
noun, plural microns, micra
[mahy-kruh] /ˈmaɪ krə/ (Show IPA)
1.
Also called micrometer. the millionth part of a meter. Symbol: μ, mu.
2.
Physical Chemistry. a colloidal particle whose diameter is between 0.2 and 10 microns.
3.
Physics. a very small unit of pressure, equal to that exerted by a column of mercury 1μ high.
Origin of micron
1880-1885
1880-85; < Greek mīkrón a little, noun use of neuter singular of mīkrós small; see -on1
Dictionary.com Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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British Dictionary definitions for micra

micra

/ˈmaɪkrə/
noun
1.
a plural of micron

micron

/ˈmaɪkrɒn/
noun (pl) -crons, -cra (-krə)
1.
a unit of length equal to 10–6 metre. It is being replaced by the micrometre, the equivalent SI unit
Word Origin
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
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Word Origin and History for micra

micron

n.

"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
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micra in Medicine

micron mi·cron or mi·kron (mī'krŏn')
n. pl. mi·crons or mi·cra (-krə) or mi·krons or mi·kra (-krə)

Abbr. μm See micrometer.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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micra in Science
micron
  (mī'krŏn')   
See micrometer2.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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