Modals are words that express modality. Modals function within verb phrases functioning as predicates. Only one grammatical form can perform the function of modal in English. The one grammatical form that can function as the modal is the verb. Only the modal verbs can, could, may, might, must, shall, should, will, and would and the quasi-modal verbs ought (to), had better (had best), used to, dare, and need can function as a modal.
Modality
Modality is the grammaticalized expression of the subjective attitudes and opinions of the speaker including possibility, probability, necessity, obligation, permissibility, ability, desire, and contingency.
As a semantic-grammatical category concerned with the status of the proposition that describes the event expressed by an utterance, modality might also be construed as the relativization of the validity of sentence meanings to a set of possible worlds or ways in which people could conceive the world to be different. In other words, modality allows language users to express what is, what would be, what may be, and what should be.
All languages express modality through either grammatical mood or modal systems (or both).
The English language expresses modality through grammatical mood and modal verbs.
Modal Verbs
Modal verbs are a type of auxiliary verb in English grammar. Unlike prototypical English verbs, modal verbs are both neutral and defective. The neutralization of modal verbs refers to the fact that modal verbs lack a separate third person singular simple present tense form. The defectiveness of modal verbs refers to the fact that modal verbs lack non-tensed forms. Quasi-modal verbs are a subset of modal verbs that possess some but not all grammatical properties of prototypical modal verbs. Modal verbs and quasi-modal verbs perform the grammatical function of modal. For example:
- I can work late tomorrow.
- You might want to clean your carpets.
- She would wear neon pink to a funeral.
- We need not worry so much.
- They ought to remember to lock the hallway doors.
- Marka and Shelia should never have gone to the theater.
The only grammatical form that can function as the modal in the English language is the verb, specifically the modal verbs can, could, may, might, must, shall, should, will, and would and the quasi-modal verbs ought (to), had better (had best), used to, dare, and need.
Summary
Modals in English grammar are words that express modality, which is the grammaticalized expression of the subjective attitudes and opinions of the speaker including possibility, probability, necessity, obligation, permissibility, ability, desire, and contingency.
Modal is a grammatical function.
The grammatical form that can function as the modal in English grammar is the verb phrase. The nine auxiliary verbs, or modal verbs, that can function as the modal are the verbs can, could, may, might, must, shall, should, will, and would. The five quasi-modal verbs that function as modals are ought (to), had better (had best), used to, dare, and need.
Modals are constituents of the verb phrase.
References
Brinton, Laurel J. & Donna M. Brinton. 2010. The linguistic structure of Modern English, 2nd edn. Amsterdam: John Benjamins Publishing Company.
Hopper, Paul J. 1999. A short course in grammar. New York: W. W. Norton & Company.
Huddleston, Rodney. 1984. Introduction to the grammar of English. Cambridge: Cambridge University Press.
Kilby, David. 1984. Descriptive syntax and the English verb. Dover, New Hampshire: Croom Helm.
Leech, Geoffrey N. 2004. Meaning and the English verb. Harlow, English: Pearson Longman.