Toinfinitive

The to-infinitive, or the to-infinitive form, is the non-finite verb form formed by the particle to followed by the base form of a verb (to eat, to go, to be). It is a key non-finite construction in English and is distinguished from the bare infinitive, which has no to (eat, go, be).

Uses and functions fall into several common patterns. As a subject: To err is human. As a complement: His goal is to become a doctor. As an object: I want to learn. As an adverbial phrase of purpose: She went to the store to buy milk. It can also appear in infinitive phrases that modify nouns or verbs, such as the plan to leave or an easy-to-understand explanation.

After certain verbs, adjectives, and nouns the to-infinitive is common. Verbs of desire, intention, or belief—want, hope, decide, promise, plan—are often followed by to-infinitives: I hope to see you. Adjectives like easy or difficult can take a to-infinitive: easy to understand. Nouns can govern a to-infinitive clause: the decision to leave.

A related distinction is with the bare infinitive, which follows modal verbs (can, may, must), certain causative or perception verbs (make him go), and some fixed expressions. The topic of split infinitives—placing an adverb between to and the verb (to boldly go)—is a traditional concern in style guides, though modern usage accepts it when it improves clarity or emphasis.

In syntax, to-infinitives can form infinitival clauses that function as noun, adjective, or adverb phrases and may exhibit control or raising phenomena in more advanced analyses.