Clauses of purpose

To

We can use to + infinitive to express purpose.

Example

• The student worked hard to pass the test. ✅
• The student worked hard for passing the test. ❌

In order (not) to/so as (not) to

In order to and so as to are more formal ways to express purpose in writing compared to to. All three are followed by an infinitive.

Example

• We were asked to stay in order to finish the project.
• He left home early in order not to be late.
• Use a plastic hammer so as to avoid damage.
• They walked quietly so as not to wake up the children.

For

We can also use for + noun to express purpose.

Example

• We went to the bar for a drink.
• Would you like to go to the park for a run?

So that

We can use so that + clause to express purpose. Modal verbs like could, can, or would often accompany this structure.

Example

• We left early so that we could park near the center.
• He made some flashcards so that it would be easier for his mum to remember the instructions.

In case

To express precautions, we use in case + clause.

Example

• Take the umbrella in case it rains.
• I won’t tell Ann in case she tells everyone else.

References

• Clauses of contrast and purpose - Test-English