atomus, a, um, adj., = ἄτομος. Uncut, not to be cut, indivisible: Graeci (tus) stagonian et atomum tali modo appellant, Plin. 12, 14, 32, § 62.

—Far more freq., Subst.: atomus (-os), i, f., = ἡ ἄτομος, an indivisible element. Of matter, an atom, of which particles, acc. to the doctrine of Democritus, all things are composed (the distinction between an atom, an ultimate particle of matter, and a molecule, the ultimate combination of matter, was of course unknown to the ancients; syn.: corpora, corpora parva, corpora minuta, corpuscula, Lucr., Cic.): atomi, id est corpora individua propter soliditatem, Cic. Fin. 1, 6, 17; id. Tusc. 1, 18, 42; id. N. D. 1, 20, 54; id. Fat. 11, 24; id. N. D. 1, 24, 66; id. Ac. 1, 2, 6 al.; Vitr. 2, 2; Lact. de Ira Dei, 10 (where, as in Vitr. 2, 2, acc. to several editt., it stands as masc.); Isid. Orig. 13, 2, 1 sqq.

— Of time: in atomo, after the Gr. ἐν ἀτόμῳ, in a moment, in the twinkling of an eye, Tert. Res. Carn. 42 and 51; id. adv. Marc. 3, 24; so in the Gr. Test. 1 Cor. 15, 52, but rendered in momento by the Vulg.