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

  • n. The average mass of an atom of an element, usually expressed relative to the mass of carbon 12, which is assigned 12 atomic mass units.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • n. Former term for the more specific relative atomic mass.
  • n. A term used to represent the mean relative atomic mass of an element in nature, as distinct from the relative atomic mass of a single isotope.

from the GNU version of the Collaborative International Dictionary of English

  • adj. the weight of the atom of an element as compared with the weight of the atom of hydrogen, taken as a standard.
  • n. See under Atomic, and cf. 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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