狀語從句：

　　時間狀語從句

　　引導詞：when，while，as，after，before，since，until，as soon as，before，after.

　　When you think you know nothing, then you begin to know something.

　　地點狀語從句

　　where，wherever引導。地點狀語從句與定語從句的區(qū)別，where引導定語從句時，從句前應(yīng)有一個表示地點的名詞作先行詞；而狀語從句前則無需先行詞。

　　原因狀語從句

　　Tom was late because he was badly ill yesterday.

　　引導詞有because, as, since, for，seeing (that), now (that), considering (that)，in that

　　條件狀語從句

　　引導詞：if，unless，on condition that

　　If you want to know how old a woman is, ask her sister-in-law.

　　If引導的真實條件句，虛擬條件句條件狀語從句中主句使用將來時態(tài)，而從句用一般現(xiàn)在時或現(xiàn)在完成時。