Relative clauses are sometimes also called adjectival clauses because, like adjectives, they help to describe nouns.
- The ball that I see is red
Nominal clauses take the place of nouns.
- I know that the ball is red
Adverbial clauses act like adverbs.
- I was reading when she entered.
Clauses of Reason
Adverbial clauses that justify the meaning of the clause they determine are called clauses of reason.
She left because she was in a hurry.
You won't go, since you can't.
Clauses of Purpose
Adverbial clauses that show the purpose, the objective of the subject of the verb they determine.
She left early, (so as/in order) to catch the bus.
Clauses of time
Clauses of time determine when sth happened.