An aspectual language focuses on the aspect, or duration, of the verb rather than the tense, or temporal placement. English, Latin, and most modern European derivatives are tense languages; verbs are conjugated to refer to past, present, and future time. Thus: I fuck, I will fuck, I fucked.

Sumerian, Finno-Ugric, Middle Egyptian, and Akkadian, to name a few examples, are aspectual; the verb is conjugated to refer either to momentary or continuous action. Thus, the same verbal aspect, usually referred to as the imperfective, is used for I was fucking (over a period of time), I am fucking (currently, and am continuing to do so), and I will fuck in the future (for an indeterminate amount), while another, usually called the perfective, would mean I fucked (a quickie, at one point and then stopped), I fuck (rarely present, since the statement cannot be made to refer to time contemporaneous with respect to the speaking, which would make it imperfective by the implication of duration).

Languages like Attic Greek are mixed-aspectual languages (even Latin has some remnants, such as the imperfect tense); the perfect in Greek is translated by past action with duration, while the aorist refers to past momentary action. The favorite example is always the imperative: a command to close the door is given in the aorist rather than the present, since the order "close the door" in the present would mean "continue to close the door", without reference to the termination of the act.