状语从句(Adverbial Clause)
一、时间状语从句
1. when, as, while 和whenever
when 表示某个具体的时间，可指一段时间和一点时间，可表示短暂动作，又可表示持续动作。As所表示的动作与主句动作同时发生，具有延续的含义，一般与延续性动词连用。While 只表示持续性的动作或状态，强调主句的动作在从句动作发生的过程中。Whenever指的是“任何时间”。例如：
When you arrive in London, please give us a call.
When I was watching TV, my mother suddenly came in.
3) He entered the room when (while, as) the meeting was going on.
4) While she was reading a novel, her mother was cooking the dinner.
It rains whenever he has the class.
Whenever that man says “To tell you the truth”, I suspect that he‟s about to tell a lie.
NT: 当as意为“当…时候”时，主要与表示动作或发展过程的动词连用，用于连接两个逐渐发展或演变的动作或状态。通常情况下不与表示感觉的动词，表示感情的动词，表示精神活动的动词和表示拥有的动词连用。
As the day goes on, the weather gets worse.
2．before 和after
before 引导的从句的动作通常发生在主句动作之后，如果从句是过去时，主句一般要用过去完成时。After引导的从句动作通常发生在主句动作之前，如果主句要用过去时，从句则要用过去完成时。例如：
1) The plane had taken off before he arrived at the airport.
2) After he had lived in the south for 20 years, he decided to go to seek his fortune in the north.
3) He was still tired even after he had had eight hours of sleeping.
但是如果不强调先后，或是因为从句中使用的是某个状态动词，after和before句子结构中的谓语动词也可以都用一般过去时。例如：They arrived at the cinema after the film began.
3. till 和until
这两个词的用法十分近似，都表示“直到…“，但在句首只能用until 。在肯定句中，主句要用延续性动词；在否定句中，until 或till可以和非延续性动词连用，这时until和before 同义。例如：
Not until they had finished the work did they go home.
I did not lose my confidence until I failed seven times.
I did not go to bed until my mother came back.
We ran and ran, till I thought my heart would burst.
4．as long as, every time, each time, next time
as long as表示“只要”；every time 表示“每次”；each time表示“每逢”；next time 表示“下次”，它们可以直接引导句子。
1）I am happy as long as my children are.
2) He will continue working as long as he has the strength.
She will not sit so long as she can lie on the bed.
She smiles every time she sees me.
I am going to see him next time he comes to Shanghai.
5. once, as soon as, the instant (that), the moment(that),, the minute(that), directly 和immediately 这几个连词引导的从句都表示从句动作一发生，主句动作随即发生, 意为“一…就”。例如：
1) She came to the scene immediately she heard of the bad news.
2) They told me the news the moment they got the message.
3) Once you understand this rule, you will have no further difficulty.
4) She wept aloud as soon as she heard the news.
6. No sooner …than 和hardly (scarcely) …when
这两个连词词组都是表示主句与从句动作随即发生，意为“一…就“。主句动词用过去完成
时。如果No sooner, hardly 或scarcely位于句首，主句要倒装。例如：
1) He had no sooner entered the house then it began to rain.
2) No sooner had he entered the house, than it began to rain.
3) He had hardly gone to bed when the telephone rang.
4) Hardly had he gone to bed when the telephone rang.
二、地点状语从句
地点状语从句表示在主句中某一动作或状态发生的地点或进行的方向,这类从句通常由Where, wherever或everywhere引导,可以放在主句前,也可以放在主句后。Where指“在某个地方”，wherever指“在任何一个地方”，everywhere指“每一…地方”, 意思与wherever 相近。例如：
1) Bamboo grows well where it has plenty of rain.
2) Wherever you go, whatever you do, I will be here waiting for you..
3) Everywhere you go, I will follow you.
三、条件状语从句
1. if 和unless
if 表示正面的条件，意为“如果”，unless表示反而的条件，意为“除非，如果不”例如：
1) If you‟ve got exams tomorrow, why aren‟t you studying?
2) The sports meeting will begin tomorrow unless it rains.
NT：在条件状语从句中常用一般时表示将要发生的动作。
2. providing, provided (that), supposing, suppose (that), on condition that 和in case
这些连词（词组）意思相近，有“如果，只要，假如，假使，在…条件下”等意思。例如：
1) Y ou can arrive in Beijing earlier for the meeting provided yo u don‟t mind taking the night train.
2) On condition that the liquid is cooled still further, it will turn to a solid.
3. only if和if only
