Expressing Purpose
Use infinitive of purpose to say thy you do something
The more formal infinitive form in order to can also be used.
i went to the bank to cash a check.
i went to the bank in order to cash a check.
He wore a helmet to protect himself
He wore a helmet in order to protect himself.
Sometimes so that is used.Note thatit is followed by a subject and a verb
i'm learning English so that i can study in the United States.
i'll give you my telephone number now so that i won't forget.