Tense

In grammar, tense is a category that expresses time reference. Tenses are usually manifested by the use of specific forms of verbs, particularly in their conjugation patterns.

Basic tenses found in many languages include the past, present and future. Some languages have only two distinct tenses, such as past and non-past, or future and non-future. There are also tenseless languages, like Chinese, which do not have tense at all. 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 relativised 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 three categories are not manifested separately, some languages may be described in terms of a combined tense–aspect–mood (TAM) system.

Etymology
The English noun tense comes from Old French tens "time" (spelled temps in modern French through deliberate archaisation), from Latin tempus "time". It is not related to the adjective tense, which comes from Latin tensus, the perfect passive participle of tendere "stretch".

Uses of the term
In modern linguistic theory, tense is understood as a category that expresses (grammaticalises) time reference; namely one which, using grammatical means, places a state or action in time. Nonetheless, in many descriptions of languages, particularly in traditional European grammar, the term "tense" is applied to series of verb forms or constructions that express not merely position in time, but also additional properties of the state or action – particularly aspectual or modal properties.

The category of aspect expresses how a state or action relates to time – whether it is seen as a complete event, an ongoing or repeated situation, etc. Many languages make a distinction between perfective aspect (denoting complete events) and imperfective aspect (denoting ongoing or repeated situations); some also have other aspects, such as a perfect aspect, denoting a state following a prior event. Some of the traditional "tenses" express time reference together with aspectual information. In Latin and French, for example, the imperfect denotes past time in combination with imperfective aspect, while other verb forms (the Latin perfect, and the French passé composé or passé simple) are used for past time reference with perfective aspect.

The category of mood is used to express modality, which includes such properties as uncertainty, evidentiality, and obligation. Commonly encountered moods include the indicative, subjunctive, and conditional. Mood can be bound up with tense, aspect, or both, in particular verb forms. Hence certain languages are sometimes analysed as having a single tense–aspect–mood (TAM) system, without separate manifestation of the three categories. The term tense, then, particularly in less formal contexts, is sometimes used to denote any combination of tense proper, aspect, and mood. As regards English, there are many verb forms and constructions which combine time reference with continuous and/or perfect aspect, and with indicative, subjunctive or conditional mood. Particularly in some English language teaching materials, some or all of these forms can be referred to simply as tenses (see below).

Particular tense forms need not always carry their basic time-referential meaning in every case. A present tense form may sometimes refer to the past (as in the historical present), a past tense form may sometimes refer to the non-past (as in some English conditional sentences), and so on.

Possible tenses
Not all languages have tense: tenseless languages include Burmese, Chinese and Dyirbal. Some languages have all three basic tenses (the past, present and future), while others have only two: some have past and non-past tenses, the latter covering both present and future times (as in Japanese, and in English in some analyses), whereas others such as Greenlandic and Quechua have future and non-future. Some languages have four or more tenses, making finer distinctions either in the past (e.g. remote vs. recent past) or in the future (e.g. near vs. remote future). The six-tense language Kalaw Lagaw Ya of Australia has the remote past, the recent past, the today past, the present, the today/near future and the remote future.

A historical past tense, used for events perceived as historical, is found in, for example, the Amazonian Cubeo language.

Tenses that refer specifically to "today" are called hodiernal tenses; these can be either past or future. Apart from Kalaw Lagaw Ya, another language which features such tenses is Mwera, a Bantu language of Tanzania. It is also suggested that in 17th-century French, the passé composé served as a hodiernal past. Tenses which contrast with hodiernals, by referring to the past before today or the future after today, are called pre-hodiernal and post-hodiernal respectively. Some languages also have a crastinal tense, a future tense referring specifically to tomorrow (found in some Bantu languages); or a hesternal tense, a past tense referring spefically to yesterday (although this name is also sometimes used to mean pre-hodiernal). A tense for after tomorrow is thus called post-crastinal, and one for before yesterday is called pre-hesternal.

Another tense found in some languages, including Luganda, is the still tense, used to indicate that a state or ongoing action is still the case (or, in the negative, is no longer the case). Luganda also has tenses meaning "so far" and "not yet".

Some languages have special tense forms that are used to express relative tense. Tenses that refer to the past relative to the time under consideration are called anterior; these include the pluperfect (for the past relative to a past time) and the future perfect (for the past relative to a future time). Similarly, posterior tenses refer to the future relative to the time under consideration, as with the English "future-in-the-past": (he said that) he would go. Relative tense forms are also sometimes analysed as combinations of tense with aspect: the perfect aspect in the anterior case, or the prospective aspect in the posterior case.

Tense marking
Tense is normally indicated by the use of a particular verb form – either an inflected form of the main verb, or a multi-word construction, or both in combination. Inflection may involve the use of affixes, such as the -ed ending that marks the past tense of English regular verbs, but can also entail stem modifications, such as ablaut, as found in the strong verbs in English and other Germanic languages, or reduplication. Multi-word tense constructions often involve auxiliary verbs or clitics. Examples which combine both types of tense marking include the French passé composé, which has an auxiliary verb together with the inflected past participle form of the main verb; and the Irish past tense, where the proclitic do (in various surface forms) appears in conjunction with the affixed or ablaut-modified past tense form of the main verb.

As has already been mentioned, indications of tense are often bound up with indications of other verbal categories, such as aspect and mood. The conjugation patterns of verbs often also reflect agreement with categories pertaining to the subject, such as person, number and gender. It is consequently not always possible to identify elements that mark any specific category, such as tense, separately from the others.

A few languages have been shown to mark tense information (as well as aspect and mood) on nouns. This may be called nominal TAM.

Languages that do not have grammatical tense, such as Chinese, express time reference chiefly by lexical means – through adverbials, time phrases, and so on. (The same is done in tensed languages, to supplement or reinforce the time information conveyed by the choice of tense.) Time information is also sometimes conveyed as a secondary feature by markers of other categories, as with the Chinese aspect markers le and guo, which in most cases place an action in past time. However, much time information is conveyed implicitly by context – it is therefore not always necessary, when translating from a tensed to a tenseless language, say, to express explicitly in the target language all of the information conveyed by the tenses in the source.

Latin and Ancient Greek
Latin is traditionally described as having six tenses (the Latin for "tense" being tempus, plural tempora): Of these, the imperfect and perfect can be considered to represent a past tense combined with imperfective and perfective aspect respectively (the first is used for habitual or ongoing past actions or states, and the second for completed actions). The pluperfect and future perfect are relative tenses, referring to the past relative to a past time or relative to a future time.
 * Present (praesens)
 * Imperfect (praeteritum imperfectum)
 * Perfect (praeteritum perfectum)
 * Future (futurus)
 * Pluperfect (plus quam perfectum)
 * Future perfect (anterior futurus)

Latin verbs are conjugated for tense (and aspect) together with mood (indicative, subjunctive, and sometimes imperative) and voice (active or passive). Most forms are produced by inflecting the verb stem, with endings that also depend on the person and number of the subject. Some of the passive forms are produced using a participle together with a conjugated auxiliary verb. For details of the forms, see Latin conjugation.

The tenses of Ancient Greek are similar, but with a three-way aspect contrast in the past: the aorist, the perfect and the imperfect. The aorist was the "simple past", while the imperfective denoted uncompleted action in the past, and the perfect was used for past events having relevance to the present.

The study of modern languages has been greatly influenced by the grammar of the Classical languages, since early grammarians, often monks, had no other reference point to describe their language. Latin terminology is often used to describe modern languages, sometimes with a change of meaning, as with the application of "perfect" to forms in English that do not necessarily have perfective meaning, or the words Imperfekt and Perfekt to German past tense forms that mostly lack any relationship to the aspects implied by those terms.

English
English has only two morphological tenses: the present, as in he goes, and the past, as in he went. The present tense sometimes references the future (as in the bus leaves tomorrow), and thus may also be called the non-past (or present–future) tense. (It also sometimes references the past, however, in what is called the historical present.)

Constructions with the modal auxiliary verbs will and shall also frequently reference the future (although they have other uses as well); these are often described as the English future tense. Less commonly, forms with the auxiliaries would and (rarely) should are described as a relative tense, the future-in-the-past. (The same forms are used for the conditional mood, and for various other meanings.)

The present and past are distinguished by verb form, using either ablaut (sing(s) ~ sang) or suffix (walk(s) ~ walked). For details, see English verbs.

English also has continuous (progressive) aspect and perfect aspect; these together produce four aspectual types: simple, continuous, perfect, and perfect continuous. Each of these can combine with the tenses to produce a large set of different constructions, mostly involving one or more auxiliary verbs together with a participle or infinitive:

In some contexts, particularly in English language teaching, the tense–aspect combinations in the above table may be referred to simply as tenses. For details of the uses of these constructions, as well as additional verb forms representing different grammatical moods, see Uses of English verb forms.

Other Indo-European languages
Proto-Indo-European verbs had present, perfect (stative), imperfect and aorist forms – these can be considered as representing two tenses (present and past) with different aspects. Most languages in the Indo-European family have developed systems either with two morphological tenses (present or "non-past", and past) or with three (present, past and future). The tenses often form part of entangled tense–aspect–mood conjugation systems. Additional tenses, tense–aspect combinations, etc. can be provided by compound constructions containing auxiliary verbs.

The Germanic languages (which include English) have present (non-past) and past tenses formed morphologically, with future and other additional forms made using auxiliaries. In standard German, the compound past (Perfekt) has replaced the simple morphological past in most contexts.

The Romance languages (descendants of Latin) have past, present and future morphological tenses, with additional aspectual distinction in the past. French is an example of a language where, as in German, the simple morphological perfective past (passé simple) has mostly given way to a compound form (passé composé).

Irish, a Celtic language, has past, present and future tenses (see Irish conjugation). The past contrasts perfective and imperfective aspect, and some verbs retain such a contrast in the present. Classical Irish had a three-way aspectual contrast of simple–perfective–imperfective in the past and present tenses.

Persian, an Indo-Iranian language, has past and non-past forms, with additional aspectual distinctions. Future can be expressed using an auxiliary.

In the Slavic languages, verbs are intrinsically perfective or imperfective. In Russian and some other languages in the group, perfective verbs have past and future tenses, while imperfective verbs have past, present and future, the imperfective future being a compound tense in most cases. The future tense of perfective verbs is formed in the same way as the present tense of imperfective verbs. However, in South Slavic languages, there may be a greater variety of forms – Bulgarian, for example, has present, past (both "imperfect" and "aorist") and future tenses, for both perfective and imperfective verbs, as well as perfect forms made with an auxiliary (see Bulgarian verbs).

Other languages
Finnish and Hungarian, both members of the Uralic language family, have morphological present (non-past) and past tenses. The Hungarian verb van ("to be") also has a future form.

Turkish verbs conjugate for past, present and future, with a variety of aspects and moods.

Arabic verbs have past and non-past; future can be indicated by a prefix.

Korean verbs have a variety of affixed forms which can be described as representing present, past and future tenses, although they can alternatively be considered to be aspectual. Similarly, Japanese verbs are described as having present and past tenses, although they may be analysed as aspects. Chinese and many other East Asian languages generally lack inflection and are considered to be tenseless languages, although they may have aspect markers which convey certain information about time reference.

For examples of languages with a greater variety of tenses, see the section on possible tenses, above. Fuller information on tense formation and usage in particular languages can be found in the articles on those languages and their grammars.