The Presocratic atomist philosopher of Abdera (c. 460–c. 370 BC), founder with Leucippus of the atomic theory and source of the eidola (images) doctrine that Epicurus inherited. Cited in Fam. 15.16 as the originator, before Epicurus, of the theory of perception by images. Distinct from person:democritus-sicyonius, Cicero's Achaean guest-friend.