Infinitive

An infinitive is the base form of a verb used as a non-finite verb form. In English it is most commonly introduced by the particle to, as in to read, to go, or to be. A related form, the bare infinitive, lacks the particle to and appears after modal verbs (can, may, must), after certain verbs of perception or causation (see, hear, let, make), and in some fixed constructions (I helped him go).

Functions and uses

Infinitives can function as nouns, adjectives, or adverbs. As a noun, for example, To err is human. As an adjective, the book to read is on the desk modifies the noun. As an adverb, she studied to improve her score explains purpose. Infinitive phrases, consisting of to plus a verb and any dependents (to learn a language quickly, to arrive before noon), can act as subjects, objects, or complements.

Tense and aspect

The infinitive itself carries no tense. English forms a perfect infinitive with to have plus a past participle (to have eaten) and a perfect-continuous or passive sense with more complex forms (to have been waiting, to be going). The present or future relative timing can be conveyed through context or accompanying auxiliaries.

In other languages

Many languages have infinitives with distinct endings or morphological changes (for example, Spanish infinitivo endings -ar, -er, -ir; Italian -are, -ere, -ire). Some languages use infinitives without a particle and treat them differently from gerunds or participles.

Relation to other non-finite forms

Infinitives contrast with gerunds (verb forms ending in -ing that function as nouns) and participles (used to form finite or non-finite clauses). The term infinitive derives from Latin infinitivus.