Molecule, n.: The ultimate, indivisible unit of matter. It is distinguished from the corpuscle, also the ultimate, indivisible unit of matter, by a closer resemblance to the atom, also the ultimate, indivisible unit of matter ... The ion differs from the molecule, the corpuscle and the atom in that it is an ion.
Ambrose Bierce (2001). “The Unabridged Devil's Dictionary”, p.165, University of Georgia Press