Tense and Aspect in Morphology

Distinctions of time are among the most common notions expressed in morphology cross-linguistically. But the inventories of distinctions marked in individual languages are also varied. Some languages have few if any morphological markers pertaining to time, while others have extensive sets. Certain categories do recur pervasively across languages, but even these can vary subtly or even substantially in their uses. And they may be optional or obligatory. The grammar of time is traditionally divided into two domains: tense and aspect. Tense locates situations in time. Tense markers place them along a timeline with respect to some point of reference, a deictic center. The most common reference point is the moment of speech. Many languages have just three tense categories: past for situations before the time of speech, present for those overlapping with the moment of speech, and future for those subsequent to the moment of speech. But many languages have no morphological tense, some have just two categories, and some have many more. In some languages, morphological distinctions correspond fairly closely to identifiable times. There may, for example, be a today (hodiernal) past that contrasts with a yesterday (hesternal) past. In other languages, tense distinctions are more fluid. A recent past might be interpreted as ‘some time earlier today’ for a sentence meaning ‘I ate a banana’, but ‘within the last few months’ for a sentence meaning ‘I returned from Africa’. Languages also vary in the mobility of the deictic center. In some languages tense distinctions are systematically calibrated with respect to the moment of speaking. In others, the deictic center may shift. It may be established by the matrix clause in a complex sentence. Or it may be established by a larger topic of discussion. Tense is most often a verbal category, because verbs generally portray the most dynamic elements of a situation, but a number of languages distinguish tense on nouns as well. Aspect characterizes the internal temporal structure of a situation. There may be different forms of a verb ‘eat’, for example, in sentences meaning ‘I ate lamb chops’, ‘I was eating lamb chops’, and ‘I used to eat lamb chops’, though all are past tense. They may pick out one phase of the situation, with different forms for ‘I began to eat’, ‘I was eating’, and ‘I ate it up’. They may make finer distinctions, with different forms for ‘I took a bite’, ‘I nibbled’, and ‘I kept eating’. Morphological aspect distinctions are usually marked on verbs, but in some languages they can be marked on nominals as well. In some languages, there is a clear separation between the two: tense is expressed in one part of the morphology, and aspect in another. But often a single marker conveys both: a single suffix might mark both past tense and progressive aspect in a sentence meaning ‘I was eating’, for example. A tense distinction may be made only in a particular aspect, and/or a certain aspect distinction marked only in a particular tense. Like other areas of grammar, tense and aspect systems are constantly evolving. The meanings of markers can shift over time, as speakers apply them to new contexts, and as new markers enter the system, taking over some of their functions. Markers can shift for example from aspect to tense, or from derivation to inflection. The gradualness of such developments underlies the cross-linguistic differences we find in tense and aspect categories. There is a rich literature on tense and aspect. As more is learned about the inventories of categories that exist in individual languages and the ways speakers deploy them, theoretical models continue to grow in sophistication.