Describing purpose

To, in order to, so as to, so that.

These structures express purpose and answer the question why something is done.


To                      We use 'to + verb' to say why we do something.

                   Examples: I'm going to Ireland to visit my family.
                   I went to the post office to buy some stamps.


In order to
So as to                  
We can also use 'in order to' or 'so as to'.
Examples: I'm going to Ireland in order to visit my family.


I went to the post office so as to buy some stamps.


Note                   
 1-  'in order to' and 'so as to' are more common before stative verbs like:
          be, have, know, appear, seem, understand, etc.
 Example: she left work early in order to be at home with the children.

  2-  Before a negative infinitive, we normally use 'so as' or 'in order'.
 Example: I am leaving now so as not to be late.
 (not: I am leaving now not to be late).

3-  Do not use 'for' before the infinitive of purpose.
     Example: I phoned Jenny to invite her to dinner.

    (not: I phoned Jenny for invite her to dinner).



So that                        
This structure is also frequently used to talk about purpose.
 It is normally followed by modal such as can or will.

 Example: I am saving money so that I can buy a new car.




Exercise 1:   choose the correct word.
Exercise 2:  expressing Purpose
Exercise 3: clause of purpose