A question posed by the reading of two incomplete works, two partial translations of Plato’s Timaeus, will serve to introduce us to the study of a specific field of Latin philosophical technical vocabulary. The two translations, one by Cicero (106-43 B.C.), the other by the Neoplatonist Calcidius (4th-5th century), will allow us to analyse the same philosophical question in two different contexts, to observe how this question is expressed differently in the lexical uses of the same language, Latin, but from two different periods, from two different times. We should bear in mind, however, that both authors, by the mere fact of having undertaken the translation of the same text, may have some common objectives: at the very least, and without doubt, a certain informative zeal; probably, a desire to enrich one’s own language (a sure desire in the case of Cicero); perhaps, the pretension of becoming an essential point of reference for the later tradition (in the case of Calcidius and for the medieval Platonic tradition, certainly achieved). In the course of this work, we will be able to deduce to what extent these supposed “objectives” were achieved. But, be that as it may, what will interest us here, above all, will be to analyse the work of translating the Timaeus in itself, from a lexical point of view and sticking to the study of some of the terms that shape the discussion raised by Plato in the first half of his Timaeus.