狀語從句：

　　時(shí)間狀語從句

　　引導(dǎo)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(diǎn)狀語從句

　　where，wherever引導(dǎo)。地點(diǎn)狀語從句與定語從句的區(qū)別，where引導(dǎo)定語從句時(shí)，從句前應(yīng)有一個(gè)表示地點(diǎn)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(dǎo)詞有because, as, since, for，seeing (that), now (that), considering (that)，in that

　　條件狀語從句

　　引導(dǎo)詞：if，unless，on condition that

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

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