Greek πρόληψις (prolēpsis), plural prolēpseis; Latin anticipatio, praenotio (Cicero)
Exactly how anticipations arise, and how they differ from opinions, is one of the most debated questions about Epicurean canonics. See The Criteria of Truth.
1. Key Texts
Preconception, they [the Epicureans] say, is as it were a perception, or correct opinion, or conception, or universal 'stored notion' (i.e. memory), of that which has frequently become evident externally: e.g. 'Such and such a kind of thing is a man.' For as soon as the word 'man' is uttered, immediately its delineation also comes to mind by means of preconception, since the senses give the lead. Thus what primarily underlies each name is something self-evident. And what we inquire about we would not have inquired about if we had not had prior knowledge of it. For example: 'Is what's standing over there a horse or a cow?' For one must at some time have come to know the form of a horse and that of a cow by means of preconception. Nor would we have named something if we had not previously learned its delineation by means of preconception. Thus preconceptions are self-evident. And opinion depends on something prior and self-evident, which is our point of reference when we say, e.g., 'How do we know if this is a man?' (tr. Long & Sedley)