The infinitive is the base (dictionary) form of a verb. The full infinitive uses to + verb (to run, to eat). The bare infinitive is the verb alone (run, eat), used after modal verbs and certain other verbs.
What Is an Infinitive?
The infinitive is the most basic form of a verb — the form you would look up in a dictionary. In English it has two main forms: the full (to-) infinitive, which pairs the particle to with the base verb, and the bare infinitive, which stands alone. Every English verb has an infinitive form, and knowing when to use each type is essential at CEFR levels A2–B1.
The full infinitive serves many roles. It follows a large group of common verbs (want to, need to, decide to, hope to), expresses purpose ("She went to the shop to buy milk"), and follows adjectives in common patterns ("It is easy to forget", "I am happy to help"). The infinitive can also function as the subject of a sentence, though this is more formal and a gerund is often preferred in spoken English: "To err is human".
The bare infinitive appears after all modal verbs (can, could, will, would, shall, should, may, might, must) and after specific verbs of perception and causation: see, hear, feel, watch, let, make, and (informally) help. Understanding the distinction saves learners from the common error of adding "to" after modals: "She can to swim" is always wrong — it must be "She can swim."
An important advanced form is the perfect infinitive (to have + past participle), used to express a past action relative to another point in time: "He seems to have forgotten", "I would like to have visited Rome."
Full Infinitive vs Bare Infinitive
| Form | When to use | Examples |
|---|---|---|
| Full infinitive (to + verb) | After verbs: want, need, decide, hope, plan, promise, refuse, manage, agree, choose, expect, fail, learn, offer | I want to leave. She managed to finish. |
| Bare infinitive | After modal verbs; after let, make, help (informal) | You must go. Let her speak. He made me wait. |
| Purpose (full) | To express reason/purpose | He called to apologise. She trained hard to win. |
| After adjective | Adjective + to-infinitive | It is hard to believe. I am glad to help. |
| After question word | What/where/when/how + to | I don't know what to say. Tell me how to do it. |
| Perfect infinitive | Action prior to another time | She seems to have left already. |
Verbs Followed by Full Infinitive
| Verb | Example sentence |
|---|---|
| want | I want to study medicine. |
| decide | She decided to leave early. |
| promise | He promised to call back. |
| refuse | They refused to sign the contract. |
| manage | We managed to finish on time. |
| hope | I hope to see you soon. |
| plan | She plans to travel next year. |
| offer | He offered to help with the bags. |
Common Mistakes
Mistakes to Avoid
She can to swim very fast.
She can swim very fast. (modal verbs take bare infinitive — no 'to')
I want that she comes to the party.
I want her to come to the party. (want + object + to-infinitive)
He made me to wait outside.
He made me wait outside. ('make' takes bare infinitive after object)
She went to the shop for buying bread.
She went to the shop to buy bread. (use to-infinitive, not for + gerund, to express purpose)