from The American Heritage® Dictionary of the English Language, 4th Edition

  • n. The mass of an atom, usually expressed in atomic mass units.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • n. The mass of an atom.
  • n. atomic weight; the average mass of atoms of an element.

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

  • n. (chemistry) the mass of an atom of a chemical element expressed in atomic mass units


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