The infinitive of a verb is its basic form. 

The infinitive has two forms:

the TO-infinitive = TO + base
the zero (bare) infinitive = base

You can use an infinitive and a gerund as the subject, the complement, or the object of a sentence. However, as subjects or complements, gerunds usually sound more like normal, spoken

English, whereas infinitives sound more abstract. 

To swim is a good exercise.

Swimming is a good exercise.

Infinitives can be made negative by adding "not."

He decided not to do it.

After the following phrases we use the infinitive with TO:

1. Common verbs followed by an infinitive

Agree The bank has agreed to lend me £5,000.
Aim  I aim to be a millionaire by the time I'm 35.
Appear There appears to be some mistake.
Arrange She's arranged for her son to have swimming lessons.
Ask  I couldn't ask you to do that.
Attempt Rescue workers attempted to cut him from the crashed vehicle.
Be able We were not able to give any answers.
Beg He begged me to give him the phone number.
Begin  I began to e-mail you but got interrupted.
Can/can’t afford   We can't afford to miss this play.
Can/can’t wait I can’t wait for the guests to arrive.
Care Would you care to sit down, please?
Chance 

They chanced to be in the restaurant when I arrived.
Choose I chose to fly rather than drive.
Claim


He claims to have met the president.
Come A witness came forward to say that she had seen him that night.


Consent

  Very reluctantly, I've consented to lend her my car.
Dare Do you dare (to) tell him the news?
Decide In the end, we decided to go to the theatre.
Demand   I demand to see a doctor.
Deserve He deserves to be treated with respect.
Endeavour He endeavoured to attract the waiter's attention.
Expect He didn't expect to see me.
Fail He failed to do his duty.
Get I got to know the town really well.
Grow (up) I grew to hate my job.
Guarantee Just looking at a picture of the sea is guaranteed to make me feel sick.
Happen It happened to snow on the night she was born.
Have I have to speak to your father.
Hesitate If you need anything, don't hesitate to call me.
Hope We hope to buy a house in the spring.
Hurry  She hurried to answer the phone.
Incline 

Her attitude did not incline me to help her.
Intend We intend to go.
Learn  I'm learning to play the piano.
Long She longed to see him again.
Manage I managed to get a promotion.
Mean  I meant to go running this morning, but I overslept.
Need  You'll need to work hard to pass this exam.
Neglect He neglected to mention the fact that we could lose money on the deal.
Oblige The law does not obligate sellers to accept the highest offer.
Offer He offered to take her home in a taxi.
Ought  You ought to work harder than that.
Pay  I think we'll need to pay a builder to take this wall down.
Permit The security system will not permit you to enter without the correct password.
Plan  I'm not planning to stay here much longer.
Prepare

It seems as if she is preparing to win.
Plead He pleaded to be allowed to go.
Pledge I've been pledged to secrecy.
Promise She promises to be a fine actor.
Propose I propose to leave town now.
Prove The experiment proved to be successful.
Refuse  He refused to leave.
Remain A cure remains to be found.
Request He requested me to leave.
Seek They sought to reassure the public.
Seem   You seem to be very interested.
Start They started to work.
Strive He strives to get promotion.
Swear  He swore to do his duty.
Tend Men tend to die younger than women.
Threaten They threatened to kill him.
Use Use scissors to cut the shapes out.
Volunteer   We were volunteered to do the dishes.

Wait

 She waited for me to say something.
Want/Would like What do you want to eat?
Wish  I wish to make a complaint.

 

2. The to-infinitive is used to express the purpose of something and answer the question "Why?"

In this case TO has the same meaning as "in order to" or "so as to".

I remained there to see what would happen.

3. We often use the TO-infinitive with these adjectives after "IT" to give opinions, make a comment or judgement:

  • foolish
  • stupid
  • difficult
  • easy
  • possible/impossible
  • hard
  • right
  • wrong
  • nice
  • clever
  • silly

A common pattern for using the TO-infinitive with an adjective:

subject + to be + adjective + (for/of someone) + to-infinitive + (rest of sentence)

It is easy to play football.

It is wrong to kill animals.

It is possible for you to find a new job.

It is difficult for me to say "I love you".

4.  Sometimes the TO-infinitive gives a reason or additional information about these adjective:

  • able/unable
  • eager
  • likely/unlikely
  • ready
  • prepared
  • keen
  • due
  • willing/unwilling
  • anxious
  • sad
  • glad
  • happy/unhappy
  • proud
  • pleased
  • surprised
  • disappointed

I'm happy to hear it.

I'm glad to be here.

He is ready to go there.

5. The To-infinitive is used after the first/the last/the next:

Mike was the first to read the book.

6. Verbs followed by an infinitive without TO:

  • auxiliaries/modal verbs (can/could/may/might/must/shall/should/will/would/do)
  • Let
  • Make
  • Let's
  • See
  • Watch
  • Notice
  • Hear
  • Feel
  • Had better/would rather

Let me show you

They made us wait

I heard Mike sing a song

7. Help

Help can be followed by an infinitive without TO or a TO-infinitive:

She helped me find/to find a direction.