Atlas of Pidgin and Creole Language Structures Online

Languages may have different kinds of tense-aspect systems. Regarding tense, we look only at present and past situations; in the aspectual domain, we restrict ourselves to the opposition of perfective vs. imperfective.

A purely aspectual system only has a perfective aspect marker (possibly realized as a zero morpheme) that normally refers to perfective past situations, and an imperfective marker, which can be used both in present and past situations (ongoing process, current state or habitual situation). A purely temporal system only marks past, present, and future situations, regardless of aspect. A mixed tense-aspect system possesses both tense and aspect markers, as happens in most Romance languages (cf. French passé composé/passé simple vs. imparfait). For this value, it is not important whether tense marking is obligatory, optional or bound to certain contexts.

The difference between a purely aspect system and a mixed tense-aspect system lies above all in the domain of the imperfective aspect. In contrast to a mixed tense-aspect system, a purely aspectual system cannot mark the difference between present and past imperfective (i.e. between 'she is working' and 'she was working').

The last value is reserved for languages which do not mark tense or aspect morphologically, but lexically (usually with time adverbs), or to languages that possess only one tense or aspect marker.