Infinitive Phrases

An infinitive is the base form of a verb, usually preceded by “to” (to learn, to understand). An infinitive phrase is that infinitive together with any objects or modifiers that go with it, such as “to learn a new language” or “to finish the project on time.” Infinitive phrases are flexible: they can serve as subjects, objects, adverbials of purpose, and modifiers of nouns and adjectives, which makes them one of the most useful structures in English.

Many verbs are followed by a to-infinitive, particularly those expressing decisions, plans, hopes, and offers: want, decide, hope, agree, offer, promise, refuse, learn, manage, and plan. For example: I want to travel, she decided to leave, they agreed to help. Some of these verbs take an object before the infinitive: She asked me to wait; They persuaded him to stay. Knowing which verbs take an infinitive rather than a gerund is largely a matter of learning the common patterns.

A bare infinitive is the base form of a verb without “to”. It is used after modal verbs (You should rest, She can drive), after let and make plus an object (Let me explain; The film made me cry), and after verbs of perception when describing a complete action (I saw him leave; We heard her sing). One important exception is that in the passive voice, make takes “to”: He was made to apologise.

The infinitive of purpose explains why someone does something. The simplest form is a plain to-infinitive: I went to the shop to buy milk. For a more formal tone, use “in order to” or “so as to”: She studied hard in order to pass the exam. To express negative purpose, use “in order not to” or “so as not to”: He whispered so as not to wake the baby. Avoid using “for” plus a verb to express purpose; “I went to the shop for buying milk” is incorrect.

Yes, although it is less common in modern English than a gerund subject. You can say “To err is human,” but in everyday English we usually move the infinitive to the end and start with the empty subject “it”: It is easy to make mistakes (rather than “To make mistakes is easy”). This “it” structure sounds more natural and is very common with adjectives: It is important to arrive on time; It was kind of you to help.

A split infinitive places an adverb between “to” and the verb, as in the famous “to boldly go.” For a long time it was considered an error, but modern usage widely accepts it, especially when splitting makes the meaning clearer or the sentence flow more naturally. Compare “to really understand” (clear) with the more awkward “really to understand.” In very formal or conservative writing, some readers still prefer to avoid it, but it is not a grammatical mistake.

Some verbs take a to-infinitive (want, decide, hope), others take a gerund (enjoy, avoid, finish), and a few take either. The choice depends on the verb, and there is no single rule, so common patterns must be learned. A few verbs change meaning with each form: “remember to lock the door” (a task) differs from “remember locking the door” (a memory), and “stop to rest” (pause in order to rest) differs from “stop resting” (end the rest).

To make an infinitive negative, place “not” directly before “to”: She decided not to go; He promised not to be late; It is important not to panic. The “not” comes immediately before the whole infinitive, not between “to” and the verb. This pattern lets you express the avoidance or refusal of an action clearly.

The perfect infinitive is formed with “to have” plus a past participle: to have finished, to have seen. It refers to an action completed before the main verb's time: She seems to have left already; I am glad to have met you. It is also common after modals to talk about the past: You should have called; He must have forgotten. It expresses things that happened before the moment being described.

To express the purpose of an action with a verb, English uses the to-infinitive, not “for” plus a verb. So we say “I went to the shop to buy milk,” not “for buy milk” or “for buying milk.” We do use “for” plus a noun to show purpose (This knife is for cutting bread can also be This is a knife for bread), but when a verb expresses why someone acts, the to-infinitive is the correct and natural choice.