To explain the purpose of an action (“why?”) we can use to + infinitive, in order to + infinitive, or so that + a clause. Use “so that” when the subjects of the two parts are different or when a modal (can, will, would) is needed.
Form
| Structure | Example |
|---|---|
| to + base verb | I went out to buy bread. |
| in order to / so as to + base verb | She studied in order to pass. |
| so that + subject + can/could/will/would | I left early so that I could catch the train. |
When to use it
- Same subject: I called to ask about the job. / in order to ask…
- Different subject: She spoke slowly so that we could understand.
- Negative purpose: in order not to, so as not to, or so that … won't.
- Formal writing prefers in order to and so as to.
Examples
- I went to the shop to buy milk.
- She studied hard in order to pass the exam.
- He left early so that he wouldn't miss the train.
- I'm saving money so that I can travel.
- They spoke quietly so as not to wake the baby.
- Write it down so that you won't forget.
Common mistakes
- “For” + verb: I went there for to buy → to buy.
- A base verb after so that: so that I buy → so that I can buy.
- “So” without “that” for purpose is informal; “so” alone usually means result: It was raining, so I stayed in.