the mass of an isotope of an element measured in units formerly based on the mass of one hydrogen atom taken as a unit or on 1/16 (0.0625) the mass of one oxygen atom, but after 1961 based on 1/12 (0.0833) the mass of the carbon-12 atom. Abbreviation: at. m.
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Origin of atomic mass
First recorded in 1895–1900
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British Dictionary definitions for atomic mass
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
Medicine definitions for atomic mass
The mass of an atom, usually expressed in atomic mass units.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
Science definitions for atomic mass
The mass of a given atom or molecule, expressed in atomic mass units. Compare atomic weight. See also mass number.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.