We use the 
to-infinitive:
• to express 
purpose (to answer "Why...?"):
He bought some flowers to give to his wife.
 He locked the door to keep everyone out.
We sometimes say 
in order to or 
in order not to:
We set off early in order to avoid the traffic.
 They spoke quietly in order not to wake the children
… or we can say 
so as to or 
so as not to:
We set off early so as to avoid the traffic.
 They spoke quietly so as not to wake the children.
• after 
certain verbs (see 
verbs followed by infinitive), particularly verbs of 
thinking and 
feeling:
choose, decide, expect, forget, hate, hope, intend, learn, like,
 love, mean, plan, prefer, remember, want, would like, would love
… and verbs of 
saying:
agree, promise, refuse
They decided to start a business together.
Remember to turn the lights out.
Some verbs are followed by a 
direct object and the infinitive(
see verbs followed by infinitive):
advise, ask, encourage, invite, order, persuade, remind, tell, warn,
 expect, intend, would prefer, want, would like
She reminded me to turn the lights out.
 He encouraged his friends to vote for him.
• after certain 
adjectives.
Sometimes the 
to-infinitive gives a 
reason for the adjective:
- disappointed
 
- glad
 
- sad
 
- happy
 
- anxious
 
- pleased
 
- surprised
 
- proud
 
- unhappy
 
We were happy to come to the end of our journey
 = We were happy because we had come to the end of our journey
 John was surprised to see me
 = He was surprised because he saw me
Other adjectives with the 
to-infinitive are:
- able
 
- unable
 
- due
 
- eager
 
- keen
 
- likely
 
- unlikely
 
- ready
 
- prepared
 
- unwilling
 
- willing
 
Unfortunately I was unable to work for over a week.
 I am really tired. I’m ready to go to bed.
We often use the 
to-infinitive with these adjectives after it to 
give opinions:
- difficult
 
- easy
 
- possible
 
- impossible
 
- hard
 
- right
 
- wrong
 
- kind
 
- nice
 
- clever
 
- silly
 
- foolish
 
It’s easy to play the piano, but it’s very difficult to play well.
 He spoke so quickly it was impossible to understand him.
We use the preposition for to show who these adjectives refer to:
- difficult
 
- easy
 
- possible
 
- impossible
 
- hard
 
It was difficult for us to hear what she was saying.
 It is easy for you to criticise other people.
We use the preposition 
of with other adjectives:
It’s kind of you to help.
 It would be silly of him to spend all his money.
• As a 
postmodifier (see 
noun phrases) after abstract nouns like:
- ability
 
- desire
 
- need
 
- wish
 
- attempt
 
- failure
 
- opportunity
 
- chance
 
- intention
 
I have no desire to be rich.
 They gave him an opportunity to escape.
 She was annoyed by her failure to answer the question correctly.
• We often use a 
to-infinitive as a postmodifier after an indefinite pronoun (See 
indefinite pronouns):
When I am travelling I always take something to read.
 I was all alone. I had no one to talk to.
 There is hardly anything to do in most of these small towns.