Theoretical aspects of the studied language

Copular, auxiliary and defective verbs
The copular verb be has multiple irregular forms in the present tense: am for first person singular (which together with the subject pronoun is often contracted to I'm), is for third person singular (often contracted to 's), and are for plural and second person (often contracted to 're chiefly after the pronouns you, we, they). It also has two past tense forms: was for first and third person singular, and were for plural and second person (also used as a past subjunctive with all persons; see English subjunctive). The past participle is been, and the present participle and gerund is the regular being. The base form be is used regularly as an infinitive, imperative and (present) subjunctive.
English has a number of modal verbs which generally do not inflect (most of them are surviving preterit-present verbs), and so have only a single form, used as a finite verb with subjects of all persons and numbers. These verbs are can and could, may and might, shall and should, will and would, as well as must, ought (to), need and dare (when used with a bare infinitive), and in some analyses used (to) and had better. (The modals could, might, should and would are historically the past tense forms of can, may, shall and will respectively, though they are not always used as such.) These verbs do not have infinitive, imperative or participle forms, although in some cases there exists a synonymous phrase that can be used to produce such forms, such as be able to in the case of can and could. The negation of can is spelled as a single word, cannot. There are contracted forms 'll and 'd for will and would (in some cases possibly from shall and should).
Other verbs used as auxiliaries include have, chiefly in perfect constructions (the forms has, have and had can contract to 's, 've and 'd), and do (does, did) in emphatic, inverted and negated constructions (see do-support).

Another example of a defective verb is beware, which is used only in those forms in which be remains unchanged, namely the infinitive, subjunctive and imperative.

Archaic forms