- molecule
- 1794, "extremely minute particle," from Fr. molécule (1678), from Mod.L. molecula, dim. of L. moles "mass, barrier" (see mole (3)). A vague meaning at first; the vogue for the word (used until late 18c. only in Latin form) can be traced to the philosophy of Descartes. First used in modern scientific sense by Amedeo Avogadro (1811).