The infinitive is a non-finite verb form that names an action or state without specifying person, number, mood or tense. It is distinct from finite verb forms that agree with a subject. In many descriptions of English and other languages the infinitive appears in several shapes and serves a range of syntactic roles. For an introduction to verb forms see related verb-form material.

Characteristics

  • No subject agreement: the infinitive does not change to match person or number.
  • Non-finite: it cannot stand alone as the main predicate marking tense or mood.
  • Flexible function: can act as noun, adjective or adverb within a clause.

Forms and common examples

  • To-infinitive: to eat, to be seen, to have written.
  • Bare infinitive (no to): eat, see — used after modal verbs and some constructions.
  • Perfect infinitive: to have eaten — indicates anterior aspect relative to another point.
  • Progressive and passive infinitives: to be eating, to be seen.

Uses and syntax

Infinitives serve as subjects or objects (e.g., To learn helps; I want to learn), purpose clauses (to study), and complements after adjectives or nouns. They appear in verb patterns that differ by language: some verbs require the infinitive, others take finite clauses. Theories of control and raising describe how the understood subject of the infinitive is linked to another noun phrase.

History and cross-linguistic notes

The infinitive has roots in older Indo-European systems and shows variation: English preserves distinct to- and bare-forms, Romance languages often use infinitives as nominal forms, while other languages use verb infinitives in subordinate constructions differently. See grammatical surveys at comparative resources.

Distinctions and notable facts

Unlike gerunds or participles, infinitives are typically uninflected for tense and person although some languages mark aspect. The so-called "split infinitive" (inserting words between to and the verb) is a stylistic issue rather than a grammatical error in modern usage. For further reading consult additional references.