The most common uses of the infinitive are:
To indicate the purpose or intention of an action (where the 'to' has the same meaning as 'in order to' or 'so as to'):
- She's gone to collect her pay cheque.
- The three bears went into the forest to find firewood.
As the subject of the sentence:
- To be or not to be, that is the question.
- To know her
is to love her.
(Note: this is more common in written English than spoken)
With nouns or pronouns, to indicate what something can be used for, or what is to be done with it:
- Would you like something to drink?
- I haven't anything to wear.
- The children need a garden to play in.
After adjectives in these patterns:
- It is + adjective +to-infinitive
It is good to talk
- It is + adjective + infinitive + for someone + to-infinitive.
It is hard for elephants to see mice
- It is + adjective + infintive + of someone + to-infinitive.
It is unkind of her to say that.
After an adjective + noun when a comment or judgement is being made:
- It was a stupid place to park the car.
- This is the right thing to do.
- It was an astonishing way to behave.
With too and enough in these patterns:
too much/many (+ noun) + to-infinitive
- There's too much sugar to put in this bowl.
- I had too many books to carry.
too + adjective + to-infinitive
- This soup is too hot to eat.
- She was too tired to work.
too + adverb + to-infinitive
- He arrived too late to see the actors.
enough (+ noun) + to-infinitive
- I've had enough (food) to eat.
adjective + enough + to-infinitive
- She's old enough to make up her own mind.
not enough (+noun) + to-infinitive
- There isn't enough snow to ski on.
not + adjective + enough + to-infinitive
- You're not old enough to have grand-children!