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atomic mass

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noun Chemistry.
  1. 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.

Origin of atomic mass

First recorded in 1895–1900
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
British Dictionary definitions for atomic mass

atomic mass

noun chem
  1. the mass of an isotope of an element in atomic mass units
  2. short for relative atomic mass See atomic weight
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
atomic mass in Medicine

atomic mass

n.
  1. 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.
atomic mass in Science

atomic mass

  1. 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.