状语从句即指在主从复合句中用作状语的从句。状语从句根据其用途可分为时间状语从句、地点状语从句、原因状语从句、结果状语从句、目的状语从句、条件状语从句、方式状语从句等：
When she saw it, she turned red. 她看到它时脸红了。(时间状语从句)
He was angry because I was late. 他很生气因为我迟到了。 (原因状语从句)
If you come, he抣l be pleased. 如果你来，他会高兴的。(条件状语从句)
He was so angry that he couldnt speak. 他气得话都说不出来。(结果状语从句)
Although he is poor, hes happy. 虽然穷，但他仍很快乐。(让步状语从句)
You must do as I tell you. 你必须按我告诉你的去做。(方式状语从句)
Put it where you can reach it. 把它放在你可以拿到的地方。(地点状语从句)
Speak clearly so that they may understand you. 讲清楚些，以便他们能理解你。(目的状语从句)