Mol"e*cule (?), n. [Dim. fr. L.
moles a mass: cf. F. molécule. See 3d
Mole.] 1. One of the very small invisible
particles of which all matter is supposed to consist.
2. (Physics) The smallest part of any
substance which possesses the characteristic properties and qualities
of that substance, and which can exist alone in a free
state.
3. (Chem.) A group of atoms so united
and combined by chemical affinity that they form a complete,
integrated whole, being the smallest portion of any particular
compound that can exist in a free state; as, a molecule of
water consists of two atoms of hydrogen and one of oxygen. Cf.
Atom.