atomic mass vs relative atomic mass

atomic mass and relative atomic mass both are nouns.

Word	Noun	Adjective	Verb	Adverb
atomic mass	Yes	No	No	No
relative atomic mass	Yes	No	No	No

As nouns, atomic mass and relative atomic mass are synonyms defined as:

atomic mass and relative atomic mass: (chemistry) the mass of an atom of a chemical element expressed in atomic mass units

Other synonyms of atomic mass include atomic weight.

atomic mass (noun)	relative atomic mass (noun)
(chemistry) the mass of an atom of a chemical element expressed in atomic mass units	(chemistry) the mass of an atom of a chemical element expressed in atomic mass units