The infinitive is a form of the verb, usually used with "to". Sometimes an infinitive does not use "to" (that's why "to" is in brackets below). Infinitives look like this:

• (to) go;
• (to) do;
• (to) watch;
• (to) see; etc. 

What are infinitives?

Infinitives are a lot like -ing verbs—they are used for talking about an action, without any connection to time. For example, if I say "went", you know it is past. If I say "will do", then it is future. "Sees" is present. An infinitive has no tense: it has no time information in it. It is for talking about the idea of an action. It is not used for talking about when that action happens. Because of this, infinitives alone can never be the main verb in a sentence. These are not good English sentences:

1. Yesterday, I to go to the bank.
2. He do it now.
3. We watch a movie on Friday?
4. I to see you!

In each sentence, you need to add something, or change something, to make the sentence complete and easy to understand:

1. Yesterday, I went to the bank;
2. He should do it now;
3. We will watch a movie on Friday;
4. I can see you!

How infinitives are used

Infinitives are used in four main ways in English:

1. With "do" or another auxiliary verb as part of a verb phrase:

• Do you like music?
• I do like music!
• He might go tomorrow.
• Where should we meet?

2. As a subject or complement in a sentence:

• To work so late every night really makes me tired.
• To get par on the final hole was brilliant!
• It's nice to see you.
• The most important thing is to have fun.  

Note: Using an infinitive is not so common in English. It can sound very formal or old fashioned. However, there are many phrases that use an infinitive as a complement.

3. After a verb, adjective or noun:

• I like to eat chocolate.
• I'll wait to meet him.
• I am thrilled to see you.
• I am going to buy a book to read on the plane. 

4. To show a reason for the main action in a sentence:

• I came to ask a favour.
• He bought flowers to give to his girlfriend.