from The American Heritage® Dictionary of the English Language, 5th Edition.

  • noun A unit of length equal to one thousandth (10−3) of a micrometer or one billionth (10−9) of a meter.

from The Century Dictionary.

  • noun A unit of length (μμ) equal to 10 Ångström units, .001 microns, or .000001 millimeters: sometimes employed in microscopy or in stating wave-lengths of light.

from the GNU version of the Collaborative International Dictionary of English.

  • noun The thousandth part of a micron or the millionth part of a millimeter; -- a unit of length used in measuring light waves, etc.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

  • noun A unit of length equal to one thousandth of a micron

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • noun a metric unit of length equal to one billionth of a meter


Sorry, no etymologies found.


  • The units commonly used for this measurement are the millimicron which is denoted by the symbol uu, which equals one millioneth of a millimeter; and the Angstrom Unit (A.U.), which is one-tenth millioneth of a millimeter.



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