English Modal Verbs - Modal Verbs and Their Features

Modal Verbs and Their Features

The verbs customarily classed as modals in English have the following properties:

• They do not inflect, except insofar as some of them come in present–past (present–preterite) pairs. They do not add the ending -(e)s in the third-person singular (the present-tense modals therefore follow the preterite-present paradigm).
• They are defective: they are not used as infinitives or participles (except occasionally in non-standard English; see Double modals below), nor as imperatives, nor (in the standard way) as subjunctives.
• They function as auxiliary verbs: they modify the meaning of another verb, which they govern. This verb generally appears as a bare infinitive, although in some definitions a modal verb can also govern the to-infinitive (as in the case of ought).
• They have the syntactic properties associated with auxiliary verbs in English, principally that they can undergo subject–auxiliary inversion (in questions, for example) and can be negated by the appending of not after the verb.

The following verbs have all of the above properties, and can be classed as the principal modal verbs of English. They are listed here in present–preterite pairs where applicable:

• can and could
• may and might
• shall and should
• will and would
• must (no preterite; mote is obsolete)

Note that the preterite forms are not necessarily used to refer to past time, and in some cases are near synonyms to the present forms.

The verbs listed below mostly share the above features, but with certain differences. They are sometimes, but not always, categorized as modal verbs. They may also be called "semi-modals".

• The verb ought differs from the principal modals only in that it governs a to-infinitive rather than a bare infinitive (compare he should go with he ought to go).
• The verbs dare and need can be used as modals (Dare he fight?; You needn't go), although they are more commonly found in constructions where they appear as ordinary inflected verbs (He dares to fight; You don't need to go).
• The verb had in the expression had better behaves like a modal verb, hence had better (considered as a compound verb) is sometimes classed as a modal or semi-modal.
• The verb used in the expression used to (do something) can behave as a modal, but is more often used with do-support than with auxiliary-verb syntax: Did she use to do it? and She didn't use to do it are more common than Used she to do it? and She used not (usedn't) to do it.

Other English auxiliaries appear in a variety of inflected forms and are not regarded as modal verbs. These are:

• be, used as an auxiliary in passive voice and continuous aspect constructions; it follows auxiliary-verb syntax even when used as a copula, and in auxiliary-like formations such as be going to, is to and be about to;
• have, used as an auxiliary in perfect aspect constructions, including the idiom have got (to); it is also used in have to, which has modal meaning, but here (as when denoting possession) have only rarely follows auxiliary-verb syntax (see also must below);
• do; see do-support.

For more general information about English verb inflection and auxiliary usage, see English verbs and English clause syntax. For details of the uses of the particular modals, see Usage of specific verbs below.