to… / in order to… / so as to…

The difference between to + infinitive & in order to + infinitive

Infinitive

• basic form of a verb

• Examples: give, prevent, agree

When to & in order to are used the same

Using in order to sounds a bit more formal & explicit than to by itself. But, both are fine & common in written & spoken English.

Following two sentences have the same meaning:

• To cut the tree down, I had to buy a chainsaw

• In order to cut the tree down, I had to buy a chainsaw

Following two sentences have the same meaning:

• I went to the mall to buy clothes.

• I went to the mall in order to buy clothes.

Difference - Negative infinitive

In order to is normal before a negative infinitive but to by itself is not usually used.

Example Sentences:

• In order not to oversleep, I set the alarm for seven o'clock.

• I walked very slowly across the room with the drinks in order not to spill them.

so as to & in order to

so as to and in order to can be used interchangeably with the same level of formality & explicitness.

Example Sentences:

• We moved house last year so as to be closer to our children and grandchildren.

• I paid the cleaning lady in advance to ease her financial problems and so as not to impact her work.

Before stative verbs like know, seem, appear, understand, have, etc, it is more usual to use in order to or so as to:

• I talked to them both for half an hour so as to have a thorough understanding of the problem.

• I followed her around all day in order to know whether she had any intention of meeting him.

So that… & in order that…

These structures are also frequently used to talk about purpose, although so that is more common and less formal than in order that. Note that these structures are normally used with (modal) auxiliary verbs.

Compare the following:

• She is staying in California for two more months so that she can perfect her English.

• She is staying in California for two more months in order to perfect her English.

• We are leaving by 2:00 pm so that we don't get stuck in the rush-hour traffic.

• We are leaving by 2:00 pm so as not to get stuck in the rush-hour traffic.

• William had an afternoon nap so that he wouldn't fall asleep at the concert later.

• William had an afternoon nap in order not to fall asleep at the concert later.

• Formal: In order that you may pass the exam, I recommend you read through all your notes.

• Causal: In order to pass the exam, I recommend you read through all your notes.

In causal English, that may be omitted from the so that construction. Listen out for this variation, though I wouldn't recommend that you use it:

• I'll come early so we can have a good chat before Denise arrives.

• I've bought a video camera so I can film the children as they grow up.

• We shall wear warm clothes when we go camping in October so we don't get cold.