We use to + infinitive to say why we do something. It shows the reason.
We can only use the infinitive of purpose if:
- the subject of the main verb and the infinitive of purpose are the same.
I am calling you to ask for your help. (I’m calling you because I want to ask for your help. It’s about me.)
Common (in any tense):
I’m calling you to ask for your help.
I exercise every day to stay healthy.
I was walking to the shops to buy chocolate when I saw him.
He’s gone to the shops to buy me chocolate.
To pass this test, you need to achieve a score of 75% or more.
We use to + infinitive to say why we do something.
in order to + infinitive I’m calling in order to arrange a meeting.
so as to + infinitive (less frequent) I’m calling so as to arrange a meeting.
We went on holiday to relax.
We went on holiday in order to relax.
We went on holiday so as to relax.
Do not use
for + infinitive. We went on holiday for relax.
Negative purpose (more formal):
- with in order not to / so as not to
I got up quietly in order not to wake the baby.
He closed his bag so as not to lose the money.
- for negative purpose (even though the subjects are the same, we avoid using in order not to)
I checked the time so that I wouldn’t miss the train.
She usually writes up a shopping list so that she doesn’t forget anything.
- with CAN, COULD (to avoid using in order to be able to)
I turned on the radio so that I could hear the news.
- different subjects
I’ll leave the door open so that you can come in.
I went out so that they could prepare the party.
Final trick (to avoid SO THAT)
I left the window open so that the cat could get in
= I left the window open for the cat to get in.
She writes books so that her kids can read something nice.
= She writes books for her kids to read something nice
He worked hard so that his family could have enough money.
= He worked hard to earn enough money for his family.
- Czech ABY (Chci abys TY uvařil. Potřebuju aby ONA zůstala doma…)
I need you to help me.
I need that you help me.
I want you to stay here.
I want to that you help me.