Atom

Webster's Dictionary

(1): (n.) The smallest particle of matter that can enter into combination; one of the elementary constituents of a molecule.

(2): (n.) An ultimate indivisible particle of matter.

(3): (n.) An ultimate particle of matter not necessarily indivisible; a molecule.

(4): (n.) A constituent particle of matter, or a molecule supposed to be made up of subordinate particles.

(5): (n.) Anything extremely small; a particle; a whit.

(6): (v. t.) To reduce to atoms.