状语从句一共有9类：

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. 让步状语从句；6. 目的状语从句；7. 结果状语从句；8. 方式状语从句；9. 比较状语从句。

其中最常用的是时间状语从句。时间状语从句的引导词：时间状语从句引导词分为两部分：as，while ，when ， whenever ，before ， after ， until (till) ，since ， as soon as，every time，next time，the first/…time，the moment，the minute/…，instantly，immediately，directly(一…就…)no sooner… than…, hardly/ scarcely/ barely…when…地点状语从句引导词：地点状语从句用连接副词 where或wherever (在任何地方) 引导。原因状语从句引导词：because, as, since, now that, for,和considering that, seeing that 这七个连词都用于表示表示原因, 但在语气上一个比一个弱。条件状语从句的引导词：if, unless (除非), as / so long as (只要), on condition (只要), once ( 一旦), in case (假使) , providing / provided (that) 等。让步状语从句引导词：引导词：though, although, even if, even though,no matter + 疑问词(what/ who/ where/ when/ which/ how)，疑问词-ever (whatever, whoever, wherever, whenever, however, whichever)目的状语从句引导词：in order that …，so that，for fear that; in case; lest (以免)等。结果状语从句引导词：so, so … that, such … that; so that 等方式状语从句引导词：as, just as, as if, as though, the way (that), in the way (that)等比较状语从句引导词：as …as, not so / as … as, more…than, less … than, the more + adj. / adv., the more + adj. / adv.特殊用法：as用在不同的状语从句中意义不同：比如：

1. She sang as she worked.2. Smart as he is ,he doesn’t study hard.3. You must try to doasI did.4. She doesn’t do her work as carefully as I.5. As she was late for class, she had to say sorry.部分状语从句可使用省略形式：even if, if , once, while, though, unless, when, as if etc.1.The flower his friends gave him will die unless (it is) watered every day..2.Even if (I am) invited, I won’t go there.3.Once (you are) caught sleeping in class, you’ll be punished by your head-teacher .4.Though (he was) surprised to see us, he gave us a warm welcome.5.She won’t speak to anyone unless (she is) asked to.6.When (it is) compared with the old one, our new house is really like a palace.7.These young man volunteered to go wherever (they are) needed.