1.时间状语从句
引导时间状语从句的连词有：after，as，before，once，since，till，until，when，whenever，
now (that)，as soon as，as long as，no sooner…than等。
有些名词短语也可以引导状语从句，如：
every time，the moment，the instant. When I saw her，she was watching closely at the photo on the wall. As the sun rose，the fog dispersed. The instant he received the letter，he started off at once. Every time he went to Beijing，he used to visit the Great Wall. as，when和while都可以表示主句中动作发生的背景，也可以表示主句的动作与从句的动作同时发生，如：
As he stood there，he heard what they were talking about. I stood up and wanted to go out，when she came in. till和until在主句谓语为持续性动词的肯定式时，作“直到……为止”解，在主句谓语为瞬间动词的否定式时作“直到……才”解，如：
Let‘s wait till / until the rain stops. I did not begin work till / until he had gone. once，directly，the moment，the instant和as soon as都作“一…就”解，通常可以互换，如：
Once you understand this，you will surely make rapid progress in your study.由副词加从属连词no sooner…than，hardly / barely / scarcely…when等引导的时 间状语从句，如果no sooner，hardly，barely，scarcely前置句首，主语与谓语须用倒装结构。如：
Hardly had the film started when they came. No sooner had we reached the top of the hill than we all sat down to rest.
2. 地点状语从句
地点状语从句通常由where，wherever引导，如：
Where there is a will，there is a way. She painted wherever she happened to be.从属连词还能与any，no，every等一起构成复合句，引导地点状语从句。如：
Everywhere you go，you will be warmly welcomed.
3. 方式状语从句
引导方式状语从句的连词有as，as if，as though等，从句通常位于主句之后，如：
He had never blushed as she blushed then.(as作“按照”或“像”解。)
as if和as though都做“好像”解，两者可以互换，从句既可用陈述语气(表示可能符合事实的情况)，又可用虚拟语气(表示与事实不符的情况)，如：
I remember the whole thing as if it happened yesterday. His mother loves me as if / as though I were her daughter.
4. 条件状语从句
引导条件状语从句的连词有：if，unless，as / so long as，suppose (that)，supposing (that)，in case，when等。条件状语从句可以分为真实条件状语从句和非真实条件状语从句。
⑴真实条件句：真实条件句表示现实或可能的情况，由if引导，它的主句可以是陈述句，疑问句或祈使句，可置于主句之前或之后。
If you heat ice，it melts. If it rained，I went by bus. unless引导的否定条件状语从句，在意义上相当于if…not，如：
Don‘t come unless I telephone. as / so long as，provided / providing (that)意为“只要、如果”，如：
You can borrow this pen as long as you can keep it well. in case在英国英语中表示目的，在美国英语中可表示条件，意为“如果、万一”，如：
In case the house burns down，we‘ll get the insurance money.
⑵非真实条件句请参阅第十一章“虚拟语气”。
5.让步状语从句
引导让步状语从句的连词有：although，though，even if，even though，if，for all that，when，while，whether…or，whatever，no matter what等。
although和though意义一样，都作“虽然、即使”解，都表示让步，一般情况下可互换使用，只是although语气较重，大多置于句首。如：
They are generous though they are poor. Although he was Japanese，he spent most of his life in China. even if
和even though都作“即使”解，两者可以互换使用，如：
She insisted on her own opinion even though / even if he was wrong. if作“即使、虽然”解，也表示让步，如：
If he is wrong，he is honest. whether…or作“不论……是否”或“不论……还是”解，如：
You don‘t have to worry me whether I am well or ill.为了强调让步意义，在正式文体或文学作品中，常用as引导让步从句，从句的补语或状语置于句首。如：
Tall as he was，he couldn‘t reach the top of the shelf. Strong as you may be，you cannot lift it.词尾为-ever的wh-词可以与“no matter wh-词”互换使用，作“无论……”解，后者常用于口语中，如：
Whoever / No matter who rings，tell him I‘m out. Wherever / No matter where he is，he will be thinking of you.由whenever，wherever，however引导的从句，也可以分别看作时 间状语从句、地点状语从句和方式状语从句。把它们当作让步状语从句是因为它们常有no matter when (where，how)的含义。
6.原因状语从句
原因状语从句通常由because，since，as，when now (that)，seeing (that)，considering (that)等引导。
because，since和as三者的区别如下：
