1. 状语从句在句子中起状语作用的从句叫做状语从句。状语从句由从属连词引导。状语从句可分为：
时间状语从句：
When Susan goes to town, she will visit her grandma.
苏珊每次进程，总要去看望她奶奶。
地点状语从句：
I will go where I am needed. 哪里需要我，我就到哪里去。
方式状语从句：
I have changed it as you suggest. 我已经按照你的建议作了改变。
原因状语从句：
Mary didn’t go shopping because I advised her not to.
玛丽没有去购物，因为我劝她不要去。
目的状语从句：
They worked hard in order that they might succeed.
他们努力工作，以便能够获得成功。
结果状语从句：
Waste must be treated so that it does not become a danger to life.
废物必须进行处理，这样它才不会成为危害生命的东西。
条件状语从句：
If he works hard, he will surely succeed. 如果努力工作，他肯定会成功。
让步状语从句：
Though we are all different, we need never be separate.
比较状语从句：
I was happier than I had ever been in my life. 这是我一生中最快乐的时光。
2. 时间状语从句：after
时间状语从句由下列连词引导：After, as, before, once, since, till, until, when, whenever, while, as soon as
Let’s wait till the rain stops. 咱们等到雨停再说吧。
Once the train is moving, there’s no way to stop it.
火车一旦开动就没办法让它停下来。
They were scolded whenever they were late for school. 每次他们上学迟到都挨骂。
3. 时间状语从句：the moment
有一些表示时间的名词短语也可用来引导时间状语从句：The minute, the moment, every time, the first time
The moment he reached the country, he started his search.
他一到达这个国家，就开始他的探寻工作。
Every time I saw the straw hat, it reminded me of the tour I made years before.
每当我看到那顶草帽，它就使我想起几年前的那次旅游。
I thought her nice and honest the first time I met her。
我第一次见到她就觉得她诚实而友善。
4. 时间状语从句：directly
有一些表示时间的副词也可用来引导时间状语从句：
Directly the master came in, everyone was quiet. 校长一进来， 大家就安静下来。
The young lady rushed into the room immediately she heard the noise.
那位年轻女士一听到响声就冲进房间。
5. 时间状语从句：as的用法
1).某事一发生，另一事立即发生
As the sun rose the frog dispersed. 太阳一出来雾就消散。
They strolled into the garden as the music ceased. 音乐声一停，他们就走进花园。
2).在某事发生的过程中另一事发生
I heard the murmur of their voices as I crossed the hall. 我走过大厅的时候听到他们在嘀咕什么。(两个动作都是一般时态)
Just as he was speaking there was a loud explosion. 正当他在说话的时候，一声巨响。
(从句用进行时态)
3).两个动作同时发生
He smiled as he passed. 他路过的时候笑了一下。(两个都是短暂动作)
As she sang, the tears ran down her cheeks. 她一边唱歌，眼泪一边从脸颊淌下。
Helen heard the story as she washed. 海伦一边洗衣服一边听故事。
He saw that she was smiling as she read.
他看到她一边看着书一边笑。(两个都是延续性动作)
We get wiser as we get older.
我们随着年龄的增长而变得聪明起来。(随着时间的变化而变化)
6. 时间状语从句：when的用法
以when引导的时间状语从句中，既可用短暂性动作也可用延续性动作。
I bought the car when I received my first salary.(短暂性动作)我是在领第一笔薪水的时候买的车。
Don’t get excited when you talk.(延续性动作)说话的时候不要激动。
7. when 容易与时间状语从句混淆的例子
请注意：此项中when引导的都不是时间状语从句。
She had just finished dressing when her guests came in.
她刚刚穿戴完毕，这时她的客人进来了。
这里的when不是从属连词，而是并列连词。所以它引导的是并列句。像这类问题有以下主要特征：
when 后面的分句动词必须是瞬间动词，用于表示突然性：
We were about to start when it began to rain.正当我们要出发的时候，突然下雨了。
1).when 前面的分句是过去进行时：
He was still smiling when the door opened and his wife came in.
他正笑着，突然门开了，他的妻子走了进来。
2).when 前面的分句含有be about to, be on the point of:
He was on the point of leaving when someone knocked at the door.
他正要出发的时候，突然有人敲门。
3).when 前面的分句采用过去完成时或是过去完成进行时：
We had just fallen asleep when the telephone rang.
我们刚刚入睡，突然电话铃声响了。
The plane had been planting seed for nearly a month when it began to rain.
飞机播种了近一个月，这时天才下雨。
8. 时间状语从句：while的用法
以while引导的时间状语从句中，只能用延续性动作。
They arrived while I was sunbathing. 当我正在进行日光浴时，他们来了。
While the discussion was still going on, Mr. Zhang came in.
当讨论还在进行的时候，张先生进来了。
9. 原因状语从句
because, as, since, 用来引导原因状语从句。for虽然也是表示原因，但是它不是从属连词，而是并列连词。
because 表示最强的因果关系，表达听话者未知的原因，because引导的从句通常放在后面，表示强调时也可放在前面。because引导的从句可以用来回答Why引起的特殊疑问句。
He got the job because he was the best candidate.
他得到那份工作，因为他是最佳人选。
“Why can’t I go?”“Because you are too young.”
为什么我不能去?因为你年纪太小。
as 所表示的原因通常是听话者已经知道的。因而它不是句子的中心。不能用来回答Why引起的特殊疑问句。
As all the seats were full, he stood up. 由于所有的座位都满了，他只好站着。
Perhaps she’ll need some help, especially as she’s been ill.
她可能需要帮助，尤其是因为她一直有病。
since所表示的原因通常也是听话者已经知道的。同样since也不能用来回答Why引起的特殊疑问句。
Since you are going, I will go too. 既然你要去，我也去吧。
for 从语法分析的角度来说，它不是引导状语从句，而是构成一个并列句。 for 通常用于书面语，它通常不表示因果关系，而是对前面的分句进行补充说明。for-分句通常放在句末，for 之前有逗号。
He laughed little, for he was a sad man. 他很少发笑，因为他是个多愁的人。
She was clearly upset, for her eyes were filled with tears.
她显然心烦意乱，因为她眼眶里饱含泪水。
10. 地点状语从句
地点状语从句通常由where，wherever引导。
Where he made mistakes, he admitted these willingly.
他在什么地方做错了事，他都乐于承认这些错误。
Put it where we can see it. 把它放在我们能看得见的地方。
Let’s go wherever this path will take us.
我们就顺着这条小路走，走到哪儿就算哪儿。
