定义：
在复合句中由从句表示的状语 称作状语从句，它可以用来修 饰谓语（包括非谓语动词）、 定语或状语，或是整个句子。
准确掌握每一个连词的含义 是掌握状语从句的关键。
同时要注意主从句的时态呼应。
状语从句一般分为九大类
状语从句类别:
时间状语从句 地点状语从句 原因状语从句 目的状语从句 结果状语从句 条件状语从句 方式状语从句 比较状语从句 让步状语从句
We are cleaning the classroom while they are playing the football.
The soldier faces the powder while the beauty powder the face.
While I am washing the floor, you can be cleaning the windows.
When I opened the window, I saw him come up.
When I have time , I will go to see you.
When I came home, I met an old schoolmate of mine.
He said he would tell her about it when he saw her.
1.时间状语从句： 引导时间状语从句的连词有：
when, while, as, the moment, before, after, till, until, since, as soon as 等。
请注意 when, while, as 的区别
When ---当……时候, 通常指 某一特定的时间点，主句与从 句的动作同时发生。
Someone knocked at the door when I was having breakfast.
When I was leaving the house, the postman arrived.
When=after
When the children had gone to bed, she began to prepare her lessons.
He ran off before I could stop him.
It was not long before I forgot it all.
(It was /will be …before… 是常用句型)
After --- 在…… 之后
The customer left the ticket counter after he had a quarrel with the ticket agent.
Wh in America, we saw him twice.
While we were talking, he came in. Strike while the iron is hot.
While ---表示一种不满情绪， 意思是这边在干某种重要的事， 而另一边在享受等。
The plane took off after the air traffic controller gave clearance.
Not …until 可以和 when 互换
Before --- 在……之前
The passengers should arrive at the airport an hour before the flight departs.
Did you work as a stewardess before you come to this company?
*注意：在时间状语从句中，主 从句都是将来的动作或状态时， 习惯上主句用将来时，从句用 一般现在时。
When --- 正在……的时候，突 然…。通常主句是进行时或 be about to 时，在翻译的时候， when 可以译成没想到或突然。
I was walking along the street , when I met him.
As I was going out, it began to rain.
I saw Mary as she was going on the bus.
As he was eating his breakfast, he heard someone knock at the door.
Someone patted me on the shoulder as I was standing before the shop window.
I was about to fall asleep when my sister came in.
One evening, little Hans was sitting near the fire when he heard a loud knock at the door.
When 当从句是进行时，主句 是一般时，往往表示不满。
As --- 一边……一边, 随着 She was doing her homework as she was listening to the music.
As she grew older, she became more beautiful.
As --- 当……时，指一个动作 紧接着一个动作发生，从句通 常用进行时。
The moment --- 一……就…… =as soon as , immediately,
---Did you remember to give Mary the money you owed her?
---Yes, I gave her the moment I saw her.
Not… until --- 直到……才 He didn’t leave the office until he finished the work. =He left the office when he finished the work.