状语从句 Adverbial Clause，从句用作状语称为状语从句。根据用途，状语从句可分为时间、地点、原因、条件、方式、让步、结果、目的'等状语从句。
时间状语从句表示时间，常用的关联词有when, until, as, after, before, once, since, as long as, whenever等等。
例: 1) When you cross a main road, you must be careful.
2) He went out to play football after he had finished his homework.
3) Wait until you are called.
4) I can't recognize you. You are so changed since last we met.
5) He didn't go to school until he was eleven.
You can use my house as long as you are careful.
He is so terrible once he is drunk.
I listen to the radio while I walk every evening.
地点状语从句表示地点，常用的关联词有where, wherever, anywhere等。
例如：1) Put it where you found it.
2)Sit down wherever you like.
3)Anywhere she goes, he goes too.
原因状语从句表示原因或理由，常用的关联词有because, as, since, in case等。
1)I eat ice-cream so much because I like sweet food.
2)As I didn't know the way, I asked a policeman.
3)Since you won't help me, I'