Modality (semantics)

In language, modality is the subject concerning so-called modal auxiliary verbs like can, must, and should, that are customarily used to modify the meaning of other verbs (which in turn tend to take an infinitive form). Modal verbs express possibility (and impossibility, necessity, contingency, etc.), permissibility (and obligation, proscription, etc.), probability (and improbability, etc.). A distinction can be made between both grammatical modality and grammatical mood. Linguistic modality can also refer to the type of communication, whether vocal, signed, or written.