atomic mass unit
  • noun a unit of measurement of mass, used to express the weight of an atom or molecule and equal to one twelfth of the mass of an atom of carbon-12.
  • A Unit of mass measurement for atoms and molecules. The unit has been arbitrarily defined as 1/12 the mass of an atom of carbon-12, the most common isotope of carbon. Each unit is equal to approximately 1.6605 × 10-24 grams. Its abbreviation is amu. Also known as dalton.

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