Grammar: Clauses of purpose

Clauses of Purpose : to … / for … / so that …
a. To / in order to / so as to
• We use to + infinitive to say why somebody does something (= the purpose of an
action) :
e.g. : `Why are you going out?´ `To post a letter.´
A friend of mine phoned to invite me to a party.
I went to Paris to learn French.
• In formal English we use in order to or so as to.
e.g. : We got up early so as to have plenty of time.
I went to Paris in order to learn French.
• In negative sentences we usually use in order not to or so as not to (we don’t use
not to)
e.g. : We got up early so as not to be late or
We got up early in order not to be late.
but we don’t say:
We got up early not to be late.
b. For
• We use for + a noun to talk about the purpose of someone.
e.g. : Let’s go to the pool for a swim.
We went to a restaurant for lunch.
What would you like for dinner?
• We use for + -ing to talk about the general purpose of something , or what it is
generally used for.
e.g. : A thermometer is used for measuring temperature.
We use this knife for cutting bread.
c. So that
We also use so that for purpose.
• When the purpose is negative (so that … won’t = present / wouldn’t = past)
e.g. : We’ll leave early so that we won’t arrive late.
Saldremos temprano para no llegar tarde.
Paul has phoned his parents so that they won’t get worried.
Pablo ha llamado por telefono a sus padres para que no se preocupen.
I hurried so that I wouldn’t be late.
Me apresuré para no llegar tarde.
I hurried so that my teacher wouldn’t get angry with me.
Me apresuré para que mi profesor no se enfadara conmigo.
• When the purpose is affirmative (so that … can = present and could = past.)
e.g. : I’ll give you a key so that you can unlock the door.
Te daré una llave para que puedas abrir la puerta.
I gave you a key so that you could unlock the door.
Te dí una llave para que pudieras abrir la puerta.
• We can also use so that to answer a “Why” question.
e.g. “Why did you bring a blanket?”
“I brought a blanket so that the kids could keep warm.”
or “ I brought a blanket because I wanted the kids to keep warm.”
or “I brought a blanket so that the kids wouldn’t get cold.”
or “I brought a blanket because I didn’t want the kids to get cold.
or “I brought a blanket to *prevent the kids from getting cold.”
*to prevent someone from doing something = impedir que alguien haga algo
e.g. : He came back home early to prevent his parents from getting upset.