THE TO-INFINITIVE

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!

INFINITIVE AFTER QUESTION WORDS

These verbs: ask, decide, explain, forget, know, show, tell, understand, can be followed by a question word such as where, how, what, who, when or 'whether' + the 'to-infinitive'.

Examples:
She asked me how to use the washing machine.
Do you understand what to do?
Tell me when to press the button.
I've forgotten where to put this little screw.
I can't decide whether to wear the red dress or the black one.

The question word Why is followed by the zero infinitive in suggestions:

Examples:
Why wait until tomorrow?
Why not ask him now?
Why walk when we can go in the car?
Why not buy a new bed for your bedroom?
Why leave before the end of the game?
Why not spend a week in Beirut and a week in Baghdad?

NEGATIVE INFINITIVE
To form the negative infinitive, place not before the to- or zero infinitive:e.g. not to worry:
It's hard not to worry about exams.

Examples:
I decided not to go to London.
He asked me not to be late.
Elephants ought not to marry mice.
You'd better not smile at the crocodile.
I'd rather not eat meat.

EXAMPLES OF VERBS NORMALLY FOLLOWED BY THE INFINITIVE

We've chosen John to represent the company at the conference.
The elephant didn't mean to tread on the mouse.
We expect you to do your best in the exam.
Do you want to go to the beach?
Do you want me to go with you to the beach?
You are requested to be quiet in this library.


He claimed to be an expert.
I managed to reach the top of the hill.
I know you're only pretending to love me!
Don't pretend that you know the answer.
She failed to explain the problem clearly.
The customs man demanded to search our luggage.
I can't afford to go out tonight.


The professor challenged his students to argue with his theory.
This law empowers the government to charge more taxes.
You can't force me to do something I don't agree with.
You are obliged to drive on the left in England.
I invited the new student to have dinner with me.
What inspired you to write this poem?
The elephant told the mouse to climb up his tail.