状语从句即指在主从复合句用作状语的从句。按照其意义，状语从句可分为时间状语从句、地点状语从句、原因状语从句、目的状语从句、结果状语从句、条件状语从句、让步状语从句等。
1. 引导时间状语从句的从属连词很多，常见的有before, after, when, while, as, since, till, until, as soon as 等。
2. 表示“当…时候”的 while, when, as 的用法区别是：while从句中的谓语动词必须是延续性动词；表示带有规律性的“每当”或当主、从句谓语动词的动作发生有先后时，只能用 when；当表示“一边…一边…”或“随着”时，只能用 as。另外，用于此义的 as 所引导的时间状语从句谓语只能是动作动词，不能是状态动词。
引导条件状语从句的从属连词主要有 if, unless, as [so] long as等。
如：
Don’t come unless I telephone.
除非我打电话，否则你别来。
If you watch carefully you will see how to do it.
如果你仔细瞧你会看出该怎样做。
As long as you do your best, we’ll be happy.
只要你尽力，我们就满意了。
引导让步状语从句的从属连词主要有 although, though, however (=no matter how), even if(即使), whether…or(不论…还是)等连词。
如：
The speech is good, though it could be better.
这次演讲不错，虽然还可以再好一点。
He went out even though it was raining.
尽管下雨，他还是出去了。
引导原因状语从句的从属连词主要有because, as, since, seeing (that), now (that)等：
They can’t have gone out because the light’s on.
他们不可能出去了，因为灯还亮着。
Since you are going, I will go.
既然你去，我也去。
Now that we are alone, we can speak freely.
现在我们单独在一起，可以随便谈了。
引导地点状语从句的从属连词主要有where (在…的地方), wherever(无论什么地方), everywhere(每个…地方), anywhere(任何…地方)。
如：
I’m not living where I was.
我不在原处住了。
You can’t camp where [wherever, anywhere] you like these days.
如今你可不能随便在哪儿宿营。
Everywhere I go, I find the same thing.
不管我走到哪里，我都发现同样情况。
1. 引导目的状语从句的从属连词主要有 in order that, so that, in case, for fear等。
如：
I hired a boat so that I could go fishing.
我租了一条船去钓鱼。
Take your coat in case it rains (should rain).
带着雨衣以防下雨。
He studied hard in order that he could pass the exam.
他努力学习，是为了能通过考试。
引导结果状语从句的从属连词主要有so that, so…that, such…that等。
如：
He was so angry that he couldn't speak.
他气得话都说不出来。
He shut the window with such force that the glass broke.
他关窗子用力很大，结果玻璃震破了。
注：so…that和such…that中的that有时(尤其在口语中)可省略。