Definition of modal verb
: a verb (such as can, could, shall, should, ought to, will, or would) that is usually used with another verb to express ideas such as possibility, necessity, and permission
What is a modal verb?
A small group of auxiliary verbs, called the modal verbs (or modal auxiliary verbs, modal auxiliaries, or simply modals) are only used in combination with ordinary verbs. A modal verb changes the other verb's meaning to something different from simple fact. Modals may express permission, ability, prediction, possibility, or necessity.
The principal modal verbs are: can, could, may, might, must, ought, shall, should, will, and would.
The modal verbs are different from ordinary verbs in several ways: 1) they have no inflections at all; that is, they lack an -ing form, an -ed form, and even an -s form for the third-person singular; 2) a modal verb is always followed by the infinitive form of a verb (unless that verb has already been stated) but never follows another verb; 3) modal verbs do not follow to and are not followed by to. (Ought to, like the near-modal verb have to, is a special case.)
In their simple form, modal verbs normally refer to present or future time:
I must be nearly there by now.
I might arrive a bit later than I'd anticipated.
A trip like this can take hours more than one expects.
Word by Word Definitions
: a word that characteristically is the grammatical center of a predicate and expresses an act, occurrence, or mode of being, that in various languages is inflected for agreement with the subject, for tense, for voice, for mood, or for aspect, and that typically has rather full descriptive meaning and characterizing quality but is sometimes nearly devoid of these especially when used as an auxiliary or linking verb
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