状语从句
什么是状语？
状语修饰动词、形容词、副词或整个句子。
1. Naturally, our grandparents were pleased to get our phone call.
2. We worked hard, from sunrise to sunset.
3. To help my disabled aunt, I spend an hour working in her house every day
4. Seen from a distance, the farmhouse looked deserted.
5. I know how to light a camp fire because I had done it before.
状语的位置比较灵活，可以位于句首、句末或句中。
什么是状语从句？
状语从句指句子用作状语时，起副词作用的句子。它可以修饰谓语、非谓语动词、定语、状语或整个句子。状语从句一般由连词(从属连词)引导，也可以由词组引起。
根据其作用状语从句可分为：
1.时间状语从句
2.地点状语从句
3.原因状语从句
4.条件状语从句
5.目的状语从句
6.让步状语从句
7.比较状语从句
8.方式状语从句
9.结果状语从句
状语从句的时态特点
一般情况下，时间和条件状语从句的谓语动词一般用“一般现在时”表示“一般将来时”，用“现在完成时”表示“将来完成时”。
I will call you as soon as I arrive in Beijing.
As soon as I have finished this work, I will go home.
If he comes back, please let me know.
1．时间状语从句
常用引导词：when, as, while, as soon as, before, after, since , till, until
特殊引导词：the minute, the moment, the second, every time, the day，the instan t, immediately , directly, no sooner … than, hardly …when, scarcely … when
I didn’t realize how special my mother was until I became an adult.
While John was watching TV, his wife was cooking.
The children ran away from the orchard(果园), the moment they saw the guard
No sooner had I arrived home, then it began to rain.
Every time I listen to your advice, I get into trouble.
表示“一……就……”
除as soon as外，还有三类：
名词型——the moment, the minute, the second, the instant；
副词型——immediately, directly, instantly；
句式型——no sooner…than…, hardly/scarcely…when…
The moment I saw him, I fell in love with him.
I came immediately you called. 你一给我打电话，我就马上来。
I had no sooner got home than it began to rain. 我一到家，就开始下雨。
【注意】
如果hardly, scarcely 或no sooner置于句首，句子必须用倒装结构。
Hardly/Scarcely had I got home when it began to rain.
No sooner had I got home than it began to rain.
在时间状语从句中，不能用一般将来时、过去将来时态或将来完成时，而要用相应的一般现在时态、一般过去时或现在完成时来代替。
When, while, as(一边...一边...), after, before, as soon as, since, till /until, by the time(到。。。为止, 所在句子的主句应用完成时)
Mozart started writing music when he was four years old.
He visited a lot of places while he was traveling.
He left the classroom after he had finished his homework the other day.
when, while和as的区别
when引导的从句的谓语动词可以是延续性的动词，又可以是瞬时动词。并且when 有时表示“就在那时”, when＝and then; at that moment。
When she came in, I stopped eating.
When I lived in the countryside, I used to carry some water for him.
We were about to leave when he came in.
While引导的从句的谓语动词必须是延续性的，并强调主句和从句的动作同时发生（或者相对应）。并且while有时还可以表示对比。
While my wife was reading the newspaper, I was watching TV.
I like playing football while you like playing basketball.
As表示“一边……一边”，as引导的动作是延续性的动作，一般用于主句和从句动作同时发生；as也可以强调“一先一后。
We always sing as we walk.
As we was going out, it began to snow.
before和after引导的时间状语从句
before的本意为“在……之前”，根据具体语境还可理解为“还没来得及/还没有……就……，趁着还没……就……，不知不觉就……，……才……”等。
After表示主句动作发生在从句动作之后。
