A modal verb (also modal, modal auxiliary verb, modal auxiliary) is a type of auxiliary verb that is used to indicate modality – that is, likelihood, ability, permission, and obligation. Examples include the English verbs can/could, may/might, must, will/would, and shall/should.
In English and other Germanic languages, modal verbs are often distinguished as a class based on certain grammatical properties.
function
A modal auxiliary verb gives more information about the function of the main verb that it governs. Modals have a wide variety of communicative functions, but these functions can generally be related to a scale ranging from possibility ("may") to necessity ("must"), in terms of one of the following types of modality:
- epistemic modality, concerned with the theoretical possibility of propositions being true or not true (including likelihood and certainty)
- deontic modality, concerned with possibility and necessity in terms of freedom to act (including permission and duty)
- dynamic modality,[2] which may be distinguished from deontic modality, in that with dynamic modality, the conditioning factors are internal – the subject's own ability or willingness to act[3]
The following sentences illustrate epistemic and deontic uses of the English modal verb must:
- epistemic: You must be starving. ("It is necessarily the case that you are starving.")
- deontic: You must leave now. ("You are required to leave now.")