A to-infinitive
can be used to express purpose:
I'm studying English to find a better job.
Mary went to the door to open it.
In
order and so
as can
be used before a to-infinitive
for emphasis in
more formal styles:
The parties started negotiations so as to reach agreement as soon as possible.
They had to fly to Japan in order to meet her parents.
The negative is always in order not + to-infinitive or so as not + to-infinitive:
He tiptoed through the hall so as not to be heard.
In order not to lose time, we must act at once.
The
infinitive of purpose can only be used if the doer of
the action expressed
by the infinitive is the same as the subject of
the main clause.
If the subjects are different, we can use in
order + that-clause
or so +that-clause .
Peter works hard so that his family has everything they need.
My mother gave me a shopping list so that I wouldn't forget anything.
In
order + that-clause
is more formal and it is less common:
Our company does everything in order that all complaints are dealt with effectively.
When the verbs come and go are
used as infinitives or as imperatives,
instead of to we
use and:
I must go and check the heater.
Come and talk to him.
Go and fetch a glass.
