1. Usually we use the Infinitive with "to": to write, to drive, to walk, to decide, to travel, to play, to talk, etc.

1. She likes to write letters.

2. I asked him to walk faster.

3. I've arange to play tennis tomorrow morning.

  2. After the verbs offer, attempt, plan, refuse, promise, agree, threaten, manage, agree, attempt, arrange, hope, fail, forget, afford, dare, tend, pretend, appear, etc., the structure is usually also verb + to + infinitive

1. After the cinema we decided to take a taxi home.

2. Jane refused to lend me any money.

3. The thief got into the house because we forgot to close the window.


  3. We use the Infinitive without "to" after:

 modal verbs can, may, must, nead, should, could, would (except "ought to"):

1. I must go out.

2. You may phone me this evening.

3. He must do it now, tomorrow will be too late.

4. They should help him.

5. Peter should start at once.

6. It really a good film. You ought to go and see it. (instead of "should")

 auxiliaries verbs do/did, shall, will, etc.:

1. How many languages do you speak?

2. I didn't invite him to the party.

3. I'm tired to walk home. I think I'll get a taxi.

4. My car won't start. (="refuses to start")

5. Will you shut the door, please?

 the verbs to make (meaning "to force") and the verb to let

1. She made him do the work.

2. You make me laugh.

3. Let me help you.

4. Let me show you some of my pictures.

 the verbs see, hear, know, feel, watch, observe, etc.

1. I saw him break the vase.

2. I saw John open the window.

3. I heard them sing.

4. I heard my dauther listen to the music.

5. Have you ever known him smoke before breakfast?

 would rather, had better, cannot but, etc.

1. I'd better go.

2. I'd rather have a cup of tea.

3. Would you rather do it yourself?

  Sometimes we use "to" without Infinitive, especially after the verbs want (to), wish (to), be going to, have to (=must), ought to:

1. She was asked to do it but she didn't want to.

2. At the supermarket I bought everything I wished to.

3. - We ought to be there tomorrow afternoon. - Yes, I guess we ought (to).

  The infinitive has four tenses in the active - a Present Infinitive (to be), a Present Continuous Infinitive (to be doing), a Perfect Infinitive (to have done), a Perfect Continuous Infinitive (to have been doing), and two in the passive - Present Infinitive (to be written), Perfect Infinitive (to have been written):

1. I pretended to be reading. (=I pretended that I was reading.)

2. She appears to be writing letter.

3. You seem to have lost weight. (=it seems that you have lost weight)

4. She seems to have been ill.

5. He appeared to have been watching the TV programme for long.

6. So much of this story is yet to be written.

7. This text is believed to have been written by the same author.

Note: The Perfect Infinitive is used with verbs such as seem, believe, know, claim, expect, appear, etc.

 There are also the Modal Perfect Infinitive formed with the Modal Verbs must, can, would, should, might, could, may and the Perfect Infinitive of the main verb:

1. She must have gone to bed late.

2. You should have told me earlier.

3. I might/could have called you.

4. She can't have cooked the meal. She hates cooking.

 Infinitive (2)