Used to explain the purpose or reason for doing something, more formal than "to".
Beginning: In order to pass the exam, she studied every night.
Middle: She studied hard in order to pass the exam.
Explains the purpose or intention behind an action.
Middle: I set an alarm so I wouldn’t oversleep.
After semicolon: I was hungry; so I made a sandwich.
A more formal version of "to", used to show purpose.
Beginning: So as to avoid traffic, we left early.
Middle: They lowered prices so as to attract more customers.
Explains the purpose of an action, often followed by a clause.
Beginning: So that everyone could hear me, I spoke loudly.
Middle: I spoke loudly so that everyone could hear me.
The most common way to express purpose, especially in informal situations.
Beginning: To improve her English, she took online classes.
Middle: He left early to catch the train.
Beginning: In order to, so as to, so that, to.
Middle: In order to, so, so as to, so that, to.
After semicolon: So.