Functions
The infinitive can be used in different syntactic functions.
Subject:
To make mistakes is easy. To defrost this fridge takes ages.
The infinitive as a subject may precede the predicate. In Modern English, this is unusual in informal style. The infinitive more often follows the predicate, and the sentence opens with the introductory it, which is “a formal subject”.
It’s easy to make mistakes.
It upsets me to hear people arguing all the time.
It was good of you to phone.
Predicative:
Your task is to get across the river without being seen.
Part of a predicative:
He’s easy to amuse. She is nice to talk to.
His theory is impossible to understand. (= It’s impossible to understand his theory)
His theory is the object of to understand.
Note that we do not put a pronoun after the infinitive or preposition.
Cricket
is not very interesting to watch it.
Part of a compound verbal predicate:
She seems to be crying.
modal predicate
Who should I pay?
The cleaning is to be finished by midday.
I’m going to / intend to inform the police.
aspect predicate
Before daylight it started to drizzle.
Object:
Many verbs can be followed by an infinitive as an object, for example:
afford consent learn prefer swear
agree decide like prepare trouble
arrange except love pretend try
ask fail manage promise want
attempt forget mean propose wish
beg hate neglect refuse wait
care help offer regret
choose hesitate omit remember
claim hope plan threaten
I don’t want to see you again.
I expect to have finished by tomorrow evening.
Some of these verbs can be followed by the Objective with the Infinitive Construction or the For-to-Infinitive Construction (see next function).
I want her to be happy.
I’ve arranged for Judy to have violin lessons.
The infinitive used as an object can be preceded by “the introductory object it”.
He found it impossible to leave the child alone.
An infinitive can be used after the questions words who, what, where, etc. (but not usually why).
I wonder who to invite. (=…who I should invite).
I don’t know where to put the car.
I can’t decide whether to answer her letter.
An infinitive is used as an object after adjectives such as pleased, lucky, sorry, afraid, etc.
You were very lucky not to be killed.
Most people are afraid to hear the truth about themselves.
Part of a Complex Object (as the verbal element in the Objective with the Infinitive Construction and the For-to-Infinitive Construction, see …):
Why won’t you let me explain?
I heard her open the door and go out.
Anne asked for the designs to be ready by Friday.
Attribute:
An infinitive modifies abstract and class nouns, indefinite and negative pronouns, ordinal numerals, the adjectives next and last.
Who was the first person ever to climb Everest without oxygen?
The next to arrive was a big black snake.
I told her about my decision to leave.
I’d like something to stop my toothache.
The infinitive can express the idea of obligation, possibility, purpose, an intended effect.
Have you got a key to open this door?
The carpets to be cleaned are in the garage.
Is there any milk to put on the cornflakes?
I’ve got some letters to write (=letters that I have to write).
Take something to read on the train. (= something you can read).
Adverbial modifier:
an adverbial modifier of purpose
I sat down to rest.
To switch on, press red button.
It can be introduced by in order (more formal) and so as.
He got up early in order to have more time to pack.
I moved to a new flat so as to be near my work.
In order and so as are normal before stative verbs like be, have, know and before negative infinitives.
I watched him in order to know more about him.
I’m going to leave now so as not to be late.
an adverbial modifier of result
In this function infinitive is chiefly used after adjectives modified by enough or too.
Mr. Evans was too busy to see anyone.
You are old enough to earn your own living.
An infinitive can be used after a noun modified by enough, too much/little, etc.
There was enough light to see what I was doing.
There’s to much snow to be able to drive.
It is also found after so – Adjective – as or such – a Noun – as. The result is negative.
He was so weak as to be unable to work.
She was such a fool as to promise him money.
c) an adverbial modifier of comparison
An infinitive is introduced by the conjunction as if or as though.
She moved her hand towards his lips as if to stop him.
d) an adverbial modifier of attendant circumstances
I arrived home to find that the house had been burgled. (=…arrived and found that…)
The idea of surprise or disappointment can be emphasized by using only before the infinitive.
He spent four years getting a degree, only to learn that there were no jobs for graduates.
e) an adverbial modifier of cause
The infinitive of see and hear can explain the cause of a (false) impression. It is usually followed by you’d think or a similar expression.
To see him walk down the street, you’d never know he was blind.
To hear her talk, you’d think she was made of money.
f) parenthesis
He was rude, to say the least of it / to put it mildly.
To speak the truth, I was a little troubled.
To make matters worse, it began to rain.
To be frank, you didn’t make a very good impression.