In grammar, tense is a category that expresses time reference with reference to the moment of speaking. Tenses are usually manifested by the use of specific forms of verbs, particularly in their conjugation patterns.
The main tenses found in many languages include the past, present, and future. Some languages have only two distinct tenses, such as past and nonpast, or future and nonfuture. There are also tenseless languages, like most of the Chinese languages, though it can possess a future and nonfuture system, which is typical of Sino-Tibetan languages. Recent work by Bittner, Tonnhauser has described the different ways in which tenseless languages nonetheless mark time. On the other hand, some languages make finer tense distinctions, such as remote vs recent past, or near vs remote future.
Tenses generally express time relative to the moment of speaking. In some contexts, however, their meaning may be relativized to a point in the past or future which is established in the discourse (the moment being spoken about). This is called relative (as opposed to absolute) tense. Some languages have different verb forms or constructions which manifest relative tense, such as pluperfect ("past-in-the-past") and "future-in-the-past".
Expressions of tense are often closely connected with expressions of the category of aspect; sometimes what are traditionally called tenses (in languages such as Latin) may in modern analysis be regarded as combinations of tense with aspect. Verbs are also often conjugated for mood, and since in many cases the four categories are not manifested separately, some languages may be described in terms of a combined tense–aspect–mood (TAM) system.
The English noun tense comes from Old Frenchtens "time" (spelled temps in modern French through deliberate archaisation), from Latintempus "time". It is not related to the adjective tense, which comes from Latin tensus, the perfect passive participle of tendere "stretch".