A nonfinite verb is a derivative form of a verb unlike finite verbs. Accordingly, nonfinite verb forms are inflected for neither number nor person, and they cannot perform action as the root of an independent clause. In English, nonfinite verbs include infinitives, participles and gerunds. Nonfinite verb forms in some other languages include converbs, gerundives and supines.

Formally, nonfinite verb forms lack the three grammatical features (mood, tense and voice) that are "associated, independently or relatively, with ... the act of predication." Generally, they also lack a subject dependent. One or more nonfinite verbs may be associated with a finite verb in a finite clause: the elements of a verb catena, or verb chain.

Because English lacks most inflectional morphology, the finite and the nonfinite forms of a verb may appear the same in a given context.