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A finite verb is a form of a verb that has a subject (expressed or implied) and can function as the root of an independent clause; an independent clause can, in turn, stand alone as a complete sentence. In many languages, finite verbs are the locus of grammatical information of gender, person, number, tense, aspect, mood, and voice. Finite verbs are distinguished from non-finite verbs, such as infinitives, participles, gerunds etc., which generally mark these grammatical categories to a lesser degree or not at all, and which appear below the finite verb in the hierarchy of syntactic structure. Verbs were originally said to be finite if their form limited the possible person and number of the subject. In some languages, such as English, this does not apply.
The finite verbs are in bold in the following sentences, and the non-finite verbs are underlined:
In many languages (including English), there can be one finite verb at the root of each clause (unless the finite verbs are coordinated), whereas the number of non-finite verbs can reach up to five or six, or even more, e.g.
Finite verbs can appear in dependent clauses as well as independent clauses:
Most types of verbs can appear in finite or non-finite form (and sometimes these forms may be identical): for example, the English verb go has the finite forms go, goes, and went, and the non-finite forms go, going and gone. The English modal verbs (can, could, will, etc.) are defective and lack non-finite forms.
It might seem that every grammatically complete sentence or clause must contain a finite verb. However, sentences lacking a finite verb were quite common in the old Indo-European languages, and still occur in many present-day languages. The most important type of these are nominal sentences. Another type are sentence fragments described as phrases or minor sentences. In Latin and some Romance languages, there are a few words that can be used to form sentences without verbs, such as Latin ecce, Portuguese eis, French voici and voilà, and Italian ecco, all of these translatable as here ... is or here ... are. Some interjections can play the same role. Even in English, utterances that lack a finite verb are common, e.g. Yes., No., Bill!, Thanks., etc.
A finite verb is generally expected to have a subject, as it does in all the examples above, although null-subject languages allow the subject to be omitted. For example, in the Latin sentence cogito ergo sum ("I think therefore I am") the finite verbs cogito and sum appear without an explicit subject – the subject is understood to be the first-person personal pronoun, and this information is marked by the way the verbs are inflected. In English, finite verbs lacking subjects are normal in imperative sentences:
And also occur in some fragmentary utterances:
The relatively poor system of inflectional morphology in English often obscures the central role of finite verbs. In other languages, finite verbs are the locus of much grammatical information. Depending on the language, finite verbs can inflect for the following grammatical categories:
The first three categories represent agreement information that the finite verb gets from its subject (by way of subject–verb agreement). The other four categories serve to situate the clause content according to time in relation to the speaker (tense), extent to which the action, occurrence, or state is complete (aspect), assessment of reality or desired reality (mood), and relation of the subject to the action or state (voice).
Modern English is an analytic language (Old English is frequently presented as a synthetic language), which means it has limited ability to express the categories by verb inflection, and it often conveys such information periphrastically, using auxiliary verbs. In a sentence such as
the verb form agrees in person (3rd) and number (singular) with the subject, by means of the -s ending, and this form also indicates tense (present), aspect ("simple"), mood (indicative) and voice (active). However, most combinations of the categories need to be expressed using auxiliaries:
Here the auxiliaries will, have and been express respectively future time, perfect aspect and passive voice. (See English verb forms.) Highly-inflected languages like Latin and Russian, however, frequently express most or even all of the categories in one finite verb.
Finite verbs play a particularly important role in syntactic analyses of sentence structure. In many phrase structure grammars for instance those that build on the X-bar schema, the finite verb is the head of the finite verb phrase and so it is the head of the entire sentence. Similarly, in dependency grammars, the finite verb is the root of the entire clause and so is the most prominent structural unit in the clause. That is illustrated by the following trees:
The phrase structure grammar trees are the a-trees on the left; they are similar to the trees produced in the government and binding framework. The b-trees on the right are the dependency grammar trees. Many of the details of the trees are not important for the point at hand, but they show clearly that the finite verb (in bold each time) is the structural center of the clause. In the phrase structure trees, the highest projection of the finite verb, IP (inflection phrase) or CP (complementizer phrase), is the root of the entire tree. In the dependency trees, the projection of the finite verb (V) is the root of the entire structure.