This chapter provides an account of the Epicurean theory of language, focusing in particular on Epicurus’ account of the origins of language, as detailed at <italic>Ep. Hdt</italic>. 75–6. It identifies two forms of linguistic naturalism (‘functional’ and ‘referential’) in Epicurus’ account of the first stage of linguistic phylogeny. It goes on to describe the implications of the advent of the second, conventionalist stage for Epicurus’ linguistic naturalism. The chapter suggests that Lucretius (like Epicurus before him) may be considered a latter-day συνειδών, enlarging and improving the language via the introduction and development of new expressions for new philosophical concepts. Finally, it considers how, if at all, Epicurean linguistic norms may have been grounded in Epicurean linguistic naturalism.