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The infinitive in English

Forms and usage of the infinitive 

Index : Basic infinitive Past infinitives,
passive infinitives
or gerund?

Other points to note

The infinitive 

Definition: The active present infinitive - normally known as just "the infinitive" -  is the basic or root form of a verb. In English, it can take two forms, with or without the particle to. For example:
     live or to live,  love or to love,  think or to think.
See also: Consecutive verbs: gerund or infinitive?

Use of the infinitive

An infinitive cannot be used as the main verb of a sentence: it can only be used in a subordinate infinitive phrase or infinitive clause. Even Shakespeare's most famous expression, "To be, or not to be?" is really a subordinate clause. The full sentence is "To be, or not to be; that is the question."   or in other words: "The question is to be or not to be".

1.1. The short infinitive , without to

This is the exception. It is used notably with certain modal auxiliaries,  can, could, may, might, will, shall, could, must.  
  1.    The manager will need a holiday.
  2.    When I was younger, I couldn't read very well.
  3.    You must put on a coat, it's cold outside..
It is also found after a handful of other verbs that introduce a verb complement, in particular: dareverbs of primary perception see, hear, smell, feel, and some verbs of permission or causative verbs, notably make, let and have.  Finally there are two common words that are followed by the infinitive without to: these are rather and better, in expressions on the model I'd rather....

  1.    I dare say you've never met my brother James.
  2.    I heard him leave the office by the back door.
  3.     I felt her touch me very gently on the arm.
  4.     I can't make this car start.
  5.     I'm free!! They let me go !
  6.    The teacher had the class redo the test because he had lost the papers.
  7.     You'd better clean the kitchen before your mother gets home.
  8.     I'd rather spend my holidays at the seaside.
After verbs of perception, the second verb can alternatively be a present participle:
I heard him leave the house by the front door. or
I heard him leaving the house by the front door.
Both these structures are possible, though there may be a shade of difference between the two; normally the speaker can choose.

1.2. The full infinitive, with to

The infinitive as verbal complement.

This is the most common use of the infinitive.  The infinitive is found in many verbal complements, and notably after the following verbs (among others):
  want, wish, have, ought, like, need, hope, expect, fail, pretend, refuse, demand, apply, agree, try.
  1.    I wish to leave, and I would like to go home.
  2.    You need to see a doctor as soon as possible.
  3.    He demanded to see the manager, so I agreed to let him in.
  4.    I fully expect to finish the job by this evening.
  5.    I want you to tell me the whole story.
  6.    I'm afraid that I fail to understand what you are trying to say.

2. Past infinitives, passive infinitives

2.1. The past infinitive, active.

This is formed using the full present infinitive of the auxiliary have, with the past participle of the verb. For example: to have eaten,  to have lost. Its use is identical to that of the present infinitive.  The short form of the past infinitive, without to, is only used after modal verbs such as may, would.  (see modal verbs).
  1.    I want to have finished the job, before I go home
  2.    You need to have passed the test, or else you won't be admitted.
  3.    Uh ! You're supposed to have painted it blue, not pink !
  4.    I'd like to have seen his expression, when he opened the letter !
  5.    I may have told you before, I really can't remember.
  6.    Help! I must have left my passport in the hotel ....

2.2. Passive infinitives.

These are formed using the full present or past infinitive of the auxiliary be with the past participle of the verb. For example: to be eaten,  to have been eaten, to be found, to have been found. Their use is identical to those of the active infinitives.  The short form of the past infinitive, without to, is only used after modal verbs such as may, would.
  1.   The car needs to be cleaned before you try to sell it.
  2.   The car needs to have been cleaned before you try to sell it.
  3.    The mayor likes to be invited to official dinners.
  4.    The door appears to have been left open all night..
  5.    He seems to have been given a very good mark..
  6.    You would be given a good mark, if you worked harder.
  7.    I'm sorry, I may have been recognised.
  8.    They are very lucky, they could have been killed..

3. Infinitive or gerund?

See also: Consecutive verbs: gerund or infinitive?

 A few verbs, such as try, love, prefer, or start can take a verbal complement either in the form of an infinitive, or as a gerund, with no change of meaning. But to avoid a repetition of -ing, it is preferable to use the infinitive after a first verb in a progressive form.  

How much do you know? Do the online Infinitive or gerund quiz

4. Other points

Three verbs, forget, remember and stop have different meanings depending on whether the verb complement is in the infinitive or is a gerund.
I stopped to listen to the music = I stopped something else in order to listen to the music.
I stopped listening to the music = I finished listening to the music.
I remembered to do the shopping = I did the shopping because I remembered.
I remembered doing the shopping = I know that I did the shopping.

The infinitive as complement to an adjective.

The infinitive with to is found as the complement of certain adjectives, following a comparative adjective, or after adjectives or adverbs qualified by an adverb of degree (too, enough, so, etc).
  1.    I was pleased to see you.
  2.    It was very clever of you to win the prize.
  3.    You'd do better* to choose a different holiday altogether.
  4.    It's easier to break it than to take it apart.
  5.    The offer really was too good to be true.
  6.    It was quite hard to know who to believe.
  7.     It was so good of you to come quickly.
  8.    We got out of the building quickly enough to avoid being seen.
* Do not confuse:  You'd better finish.... with You'd do better to finish ....

Other uses of the infinitive with to :

The infinitive with to is also found as an abbreviation of the form in order to + verb:
I went home to get some sleep. or
I went home in order to get some sleep.
Just occasionally, but with a slight change of meaning, it can be found, like a gerund, as the subject of a sentence.  
To win the big contract would be a great success
or to quote a famous line by Oscar Wilde in the Importance of being Earnest
To lose one parent, Mr Worthing, may be regarded as a misfortune; to lose both looks like carelessness.
But this is relatively formal style, and also XIXth century English.

The infinitive in indirect questions :

The infinitive can also be used to report simple questions in which the interrogative word (i.e. what or where, etc.) is the direct object of a modal auxiliary  do, can or should referring to future time, and where the original direct question is in the first person :
"How can I get to Bristol?"  ► He asked me how he could get to Bristol,
or : He asked me how to get to Bristol.
"What do we see next?"  ► They asked what they should see next,
or : They asked what to see next.

Split infinitives

See dedicated page: Split infinitives

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L'infinitif et l'impératif en anglais

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Gerunds, participles and -ing forms
The infinitive
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Adjective order in English
The possessive
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Relative clauses in English
Conditional clauses in English
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The short story of English
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