The Lucretius cited in Cicero's letters is twofold: the poet (T. Lucretius Carus, c. 99-55 BC), whose newly-published De rerum natura Cicero comments on as showing both ingenium and ars (Ad Q. fr. 2.9.3); and a contemporary M. Lucretius, friend of Cassius and informant from Capua at the outbreak of the civil war (Ad Att. 7.24-25). The first appearance in this glossary is the poet.