Verb

==Tense, aspect, and modality==
{{main|Grammatical tense|Aspect (linguistics)|Linguistic modality|Tense–aspect–mood}}
[[File:Conjugation of verb-es.svg|thumb|A single-word verb in [[Spanish language|Spanish]] contains information about time (past, present, future), person and number. The process of grammatically modifying a verb to express this information is called [[Grammatical conjugation|conjugation]].]]

Depending on the language, verbs may express ''grammatical tense'', ''aspect'', or ''modality''. 

=== Tense ===
Grammatical tense<ref>Comrie, Bernard, ''Tense'', Cambridge Univ. Press, 1985.</ref><ref name="Dahl">[[Östen Dahl]], ''Tense and Aspect Systems'', Blackwell, 1985.</ref><ref>Fleischman, Suzanne, ''The Future in Thought and Action'', Cambridge Univ. Press, 1982.</ref>  is the use of [[auxiliary verb]]s or [[inflection]]s to convey whether the action or state is before, simultaneous with, or after some reference point.  The reference point could be the [[time of utterance]], in which case the verb expresses [[absolute tense]], or it could be a past, present, or future time of reference previously established in the sentence, in which case the verb expresses [[relative tense]].

=== Aspect ===
Aspect<ref name="Dahl" /><ref>Comrie, Bernard, ''Aspect'', Cambridge Univ. Press, 1976.</ref> expresses how the action or state occurs through time. Important examples include:
*[[perfective aspect]], in which the action is viewed in its entirety through completion (as in "I saw the car")
*[[imperfective aspect]], in which the action is viewed as ongoing; in some languages a verb could express imperfective aspect more narrowly as:
**habitual aspect, in which the action occurs repeatedly (as in "I used to go there every day"), or
**[[continuous aspect]], in which the action occurs without pause; continuous aspect can be further subdivided into
***[[Stative verb|stative aspect]], in which the situation is a fixed, unevolving state (as in "I know French"), and
***[[progressive aspect]], in which the situation continuously evolves (as in "I am running")
*[[perfect (grammar)|perfect]], which combines elements of both aspect and tense and in which both a prior event and the state resulting from it are expressed (as in "he has gone there", i.e. "he went there and he is still there")
*[[discontinuous past]], which combines elements of a past event and the implication that the state resulting from it was later reversed (as in "he did go there" or "he has been there", i.e. "he went there but has now come back")<ref>[[Vladimir Plungian|Plungian, Vladimir A.]] & Johan van der Auwera (2006), [https://www.academia.edu/1761770/Towards_a_typology_of_discontinuous_past_marking "Towards a typology of discontinuous past marking"]. Sprachtypol. Univ. Forsch. (STUF), Berlin 59, 4, 317–349.</ref>

Aspect can either be [[lexical aspect|lexical]], in which case the aspect is embedded in the verb's meaning (as in "the sun shines", where "shines" is lexically stative), or it can be grammatically expressed, as in "I am running."

=== Mood and modality ===
Modality<ref>Palmer, F. R., ''Mood and Modality'', Cambridge Univ. Press, 2001.</ref> expresses the speaker's attitude toward the action or state given by the verb, especially with regard to degree of necessity, obligation, or permission ("You must go", "You should go", "You may go"), determination or willingness ("I will do this no matter what"), degree of probability ("It must be raining by now", "It may be raining", "It might be raining"), or ability ("I can speak French"). All languages can express modality with [[adverb]]s, but some also use verbal forms as in the given examples. If the verbal expression of modality involves the use of an auxiliary verb, that auxiliary is called a [[modal verb]]. If the verbal expression of modality involves inflection, we have the special case of [[grammatical mood|mood]]; moods include the [[indicative mood|indicative]] (as in "I am there"), the [[subjunctive mood|subjunctive]] (as in "I wish I ''were'' there"), and the [[imperative mood|imperative]] ("Be there!").