Modality (grammar)

In linguistics, modality is a feature of language that allows for communicating things about, or based on, situations which need not be actual. More precisely, modality is signaled by grammatical expressions (moods) that express a speaker's general intentions (or illocutionary point) as well as the speaker's commitment to how believable, obligatory, desirable, or actual an expressed proposition is.

Sometimes, the term mood is used to refer to both mood and modality, however, the two can be distinguished according to whether they refer to the grammatical expressions of various modalities (mood) or the meanings so expressed (modality). Modality can also be considered equivalent to the idea of illocutionary force if the kinds of expressions which can express modal meanings also include lexical items such as performative verbs.

Modality is closely intertwined with other linguistic phenomena such as tense and aspect, evidentiality, conditionals, and others. As with other areas of linguistics, modality has been studied extensively from typological as well as formal perspectives.

An important distinction within linguistic modality is the distinction between epistemic and deontic modality. Generally speaking, epistemic modality has to do with possibility and necessity with regard to knowledge, whereas deontic modality has to do with permission and obligation according to some system of rules. The difference between the two is illustrated in the English example below:

The sentence in (1) might be spoken by someone who has decided that all of the relevant facts in a particular murder investigation point to the conclusion that Agatha is the killer, even though it may or may not actually be the case. In contrast, (2) might be spoken by someone who has decided that, according to some standard of conduct, Agatha has committed a vile crime, and therefore the correct course of action is to kill Agatha. Note also that, although English must is ambiguous between these two interpretations, the form of the other elements in the sentences helps to disambiguate.

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