The system of expression of temporal relations is one where languages differ in the particular semantic notions they choose to bundle together and mark in their grammatical structure. To the extent that time cannot be conceived of independent of its contents, namely events, the distinctions that are grammaticalized concern the different relations that one construes between events themselves or between events and the self. The former involve the location of events on the time line relative to one another. The latter, on the other hand, express either the subjective perspective taken with regard to the temporal constituency of the event, or the subjective attitude adopted towards the truth or normative value of the proposition referring to the event. The domain of grammatical systems which provide formal means for the expression of such diverse relations has come to be treated under the rubric of tense-aspect-modality systems in the study of languages.

Overview of theoretical treatments of tense, aspect and modality

In traditional grammar, TENSE refers to the relating of the time of the referent situation to either the time of utterance or to the time of some other situation. It is also recognized that the primary characteristic of tense is that it is a deictic category. Temporal reference in language requires that interlocutors be able to control and interrelate at least two different frames of reference: the deictic and the nondeictic.