Grammar Reference

Syntax

Purpose clauses

We use purpose clauses to indicate the purpose of an action.

There are two kinds of purpose clauses: non-finite clauses and finite clauses.

Non-finite purpose clauses are the most common and contain to + infinitive. Common conjunctions used in non-finite purpose clauses are: to, in order to and so as to.

The subject of a non-finite clause is the same as the subject of the main clause. To make the sentences negative we put not in front of the to.

But we can't negate a sentence that contains only to + infinitive.

We can, however, express these ideas by:

- changing the sentence.

-using a finite clause.

Finite purpose clauses usually contain that + clause and they usually contain a modal.

Common conjunctions used in finite purpose clauses are so, so that and in order that.

If the verb in the main clause is in the present or present perfect tense, we usually use the modals can, may, will or shall in the purpose clause.

If the verb in the main clause is in the past tense, we usually use could, might, or would in the purpose clause.

We sometimes use ordinary verbs in the purpose clause, usually in negative purpose clauses.

In negative purpose clauses in case can also be used.