Atomic weights refer to the mass of an atom in atomic mass units (amu). Synonyms for atomic weights could include atomic mass, relative atomic mass, and atomic weight average. Atomic mass refers to the mass of an atom in amu, while relative atomic mass indicates the mass of an atom in comparison to a reference, usually carbon-12. The term atomic weight average is used when referring to the weighted average of the atomic masses of all isotopes of an element. Other synonyms for atomic weights could include element mass, element weight, or atomic mass number, which represents the total number of protons and neutrons in an atom.