a.m. (Adjective) — Before noon.
a.m. (Noun) — Modulation of the amplitude of the (radio) carrier wave.
a.m. (Noun) — A master's degree in arts and sciences.
a.m. (Noun) — A radioactive transuranic metallic element; discovered by bombarding uranium with helium atoms.
a.m. (Adverb) — (Latin) before noon. ex. "let's meet at 11 A.M."