‘Aspects’ have to do, not with the location of an event in time, but with its temporal distribution or contour. They show contrasts of meaning of the following sorts: “He is singing,” “He has been singing,” “He sings habitually,” “He sings repeatedly,” [...].
- Hockett (1958), a pag.237

Two of the inflectional categories of Latin verbs are ‘voice’ and ‘aspect’. There are two voices and two aspects, ‘imperfective’ and ‘perfective’. The two voices and the two aspects would be expected to intersect to yeld four combinations: active, passive imperfective, and so on.
- Hockett (1958), a pag.212