- 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
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
Examples from the Web for micra
Historical Examples of 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
Word Origin for micron
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.