In the English language, modal verbs are a type of auxiliary verb. The key way to identify a modal verb is by its defectiveness, in other words, it has neither a participle nor an infinitive. In addition, modal verbs do not take the inflection -s or -es in the third person singular, unlike other verbs.
The modal verbs in English are as follows, paired as present and preterite forms.
- shall and should
- will and would
- may and might
- can and could
- must (no preterite form in modern English)
Note that use of the preterite forms does not necessarily refer to past time, and in many cases, are considered near synonyms to the present forms.
The following have also been categorized by some as modal verbs:
- ought (to)
- had better
Note that dare and need are much more commonly used as non-modal verbs, taking -s in the third person singular and having an infinitive and past and present participles. Further, some authors do not mention had better and explicitly reject ought (to) on the grounds that the main verb infinitive is required to include the particle to.
The following are not modal verbs although they have some similar characteristics:
- used to
- be going to
- have to