Infinitives

An infinitive is the word to followed by the base form of a verb, such as to buy, to eat, or to run. Infinitives are used to explain a purpose or to complete the meaning of certain verbs.

What You'll Learn

• What an infinitive is and how to form one (to + base verb)
• How to use infinitives to explain why someone does something (infinitive of purpose)
• How to use infinitives after common verbs like want, need, like, and try
• How to spot and avoid common mistakes with infinitives

When to Use

1. To explain a purpose (why): "She went to the shop to buy some milk." (Why did she go? To buy milk.)
2. After "want": "I want to read a new book this weekend."
3. After "need": "We need to finish our homework before dinner."
4. After "like": "He likes to swim at the community pool every Saturday."
5. After "try": "She tried to reach the top shelf, but it was too high."

How to Form

Building an Infinitive

An infinitive is always to + the base form of the verb. The base form never changes, no matter what the subject or tense is.

Infinitive of Purpose

The infinitive of purpose answers the question "Why?" or "What for?". It explains the reason for an action.

Infinitive After Common Verbs

Some verbs are followed by an infinitive to complete their meaning.

Key Rules

1. Always use the base form after "to": The verb after "to" never changes. Say "She wants to go," not "She wants to goes" or "She wants to going."

2. Do not leave out "to": These verbs need "to" before the next verb. Say "I want to eat," not "I want eat."

3. The infinitive of purpose can replace "because": "He ran to the gate to catch the bus" means the same as "He ran to the gate because he wanted to catch the bus."

4. "In order to" is a longer way to show purpose: You can say "She studied hard in order to pass the test." This means the same as "She studied hard to pass the test." Both are correct, but "to + verb" is simpler.

5. Do not confuse "to" (infinitive) with "to" (preposition): In "I want to eat," the word "to" starts an infinitive. In "I walked to school," the word "to" is a preposition showing direction. An infinitive always has a verb right after "to."

6. Negative infinitives use "not to": To make an infinitive negative, place "not" before "to." "The teacher told us not to run in the corridor."

Common Mistakes

Clue Words

Verbs that are followed by an infinitive

want, need, like, try, hope, learn, decide, plan, choose, agree, wish, would like, promise, offer, refuse

Purpose signal words

why, what for, the reason, in order to, so as to

When you see any of these verbs or purpose signals, the next verb will usually be an infinitive (to + base verb).

Tip: If someone asks "Why?" and your answer starts with a verb, put "to" in front of it. Why did she go to the shop? To buy bread. This "to" shows the purpose.

Practice Tips

1. The "Why?" test for purpose: After reading a sentence, ask "Why?" If you can answer with "to + verb," the sentence uses an infinitive of purpose. "He ran to the bus stop." Why? "To catch the bus."

2. The base-form check: After writing "to," check that the verb is in its simplest form. It should not end in -s, -ed, or -ing. "To eat" is correct. "To eats," "To ate," and "To eating" are all wrong.

3. Try adding "in order" before "to": If you can add "in order" before "to" and the sentence still makes sense, you are using an infinitive of purpose correctly. "She woke up early (in order) to prepare breakfast." This works, so the infinitive is correct.

4. Spot the verb + to + verb pattern: When you see a main verb followed by "to" and another verb, check whether the first verb is one that takes an infinitive (want, need, like, try, hope, learn, decide). If it is, you have found the correct pattern.

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