A
to-infinitive can be used to express purpose:
I'm
calling to place an order for delivery.
Diya
went to the door to open it.
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In
order and so as can be used before a to-infinitive for emphasis in more formal
styles:
He
took a book with him in order to have something to read on the train.
The
parties started negotiations so as to reach an agreement as soon as possible.
In
order to attract a wider audience, we need to rethink our marketing strategy.
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 so + that-clause with the present simple tense or
with the modal verbs may, can, will, might, could or would:
Jerry
works hard so that his family has everything they need.
I'll
leave the door open so that you can come in.
Tina
gave me a shopping list so that I wouldn't forget anything.
In
order + that-clause is also possible in this case; however, it is more formal
and less common. In the that-clause, we can use the modal verbs may, shall,
might or should:
Our
company does everything in order that all complaints may be dealt with fairly
and effectively.
With
come and go, we can use the infinitive of purpose with the verb in any present
or past tense or with the gerund form of the verb:
I'm
just coming to help.
We
went to talk to a lawyer.
Have
you thought of going to see a doctor?
But if
come and go are used as infinitives or as imperatives, we use and instead of
to:
I must
go and check the heater.
He
will come and dance with you.
Go and
fetch a glass.
