A nonfinite verb, in contrast to a finite verb, is a derivative form of a verb that lacks inflection (conjugation) for number or person. In the English language, the nonfinite verb cannot perform action as the main verb of an independent clause, while in French, the first verb is typically the only finite one. In English, nonfinite verbs include infinitives, participles and gerunds. Nonfinite verb forms in some other languages include converbs, gerundives and supines. The categories of mood, tense, and or voice may be absent from non-finite verb forms in some languages.
Because English lacks most inflectional morphology, the finite and the nonfinite forms of a verb may appear the same in a given context.
Examples
In the following sentences, the non-finite verbs are emphasized, while the finite verbs are underlined. Verbs appear in almost all sentences. This sentence is illustrating finite and non-finite verbs. The dog will have to be trained well. Tom promised to try to do the work.
The case has been intensively examined today. What did they want to have done about that? Someone tried to refuse to accept the offer. Coming downstairs, she saw the man running away. I am trying to get the tickets.
In the above sentences, been, examined and done are past participles, want, have, refuse, accept and get are infinitives, and coming, running and trying are present participles (for alternative terminology, see the sections below).
In languages like English that have little inflectional morphology, certain finite and nonfinite forms of a given verb are often identical, e.g.
a. They laugh a lot. - Finite verb (present tense) in bold
b. They will laugh a lot. - Nonfinite infinitive in bold
a. Tom tried to help. - Finite verb (past tense) in bold
b. Tom has tried to help. - Nonfinite participle in bold
Despite the fact that the verbs in bold have the same outward appearance, the first in each pair is finite and the second is nonfinite. To distinguish the finite and nonfinite uses, one has to consider the environments in which they appear. Finite verbs in English usually appear as the leftmost verb in a verb catena. For details of verb inflection in English, see English verbs.
Categories
English
In English, a nonfinite verb may constitute: an infinitive verb, including the auxiliary verb have as it occurs within a verb phrase that is predicated by a modal verb. a participle. a gerund.
Each of the nonfinite forms appears in a variety of environments.
Infinitive
The infinitive form of a verb is considered the canonical form listed in dictionaries. English infinitives appear in verb catenae if they are introduced by an auxiliary verb or by a certain limited class of main verbs. They are also often introduced by a main verb followed by the particle to (as illustrated in the examples below). Further, infinitives introduced by to can function as noun phrases or even as modifiers of nouns. The following table illustrates such environments:
{ | class="wikitable" |- ! Infinitive !! Introduced via auxiliary verb !! Introduced via causative verb !! Introduced via finite verb plus to !! Functioning as noun phrase !! Functioning as an adjective |- | laugh || Do not laugh! || That made me laugh. || I tried not to laugh. || To laugh would have been unwise. || the reason to laugh |- | leave || They may leave. || We let them leave. || They refused to leave. || To leave was not an option. || the thing to leave behind |- | expand || You should expand the explanation. || We had them expand the explanation. || We hope to expand the explanation. || Our goal is to expand. || the effort to expand |}
Participle
English participles can be divided along two lines: according to aspect (progressive vs. perfect/perfective) and voice (active vs. passive). The following table illustrates the distinctions:
{ | class="wikitable" |- ! Participle !! Progressive active participle !! Progressive passive participle !! Perfect active participle !! Perfect passive participle |- | fix || The guy is fixing my bike. || I saw the guy fixing my bike. || He has fixed my bike. || My bike was fixed. |- | open || The flower was opening up. || I saw the flower opening up. || The flower has opened up. || The flower has been opened up. |- | support || The news is supporting the point. || She watched the news supporting the point. || The news has supported the point. || I understood the point supported by the news |- | drive || She is driving our car. || I watched her driving our car. || She has driven our car. || Our car should be driven often. |}