从句是有完整的句子结构的。
从句虽不能单独成句，但它也有主语部分和谓语部分。从句须由
关联词(connective)引导。
引导从句的关联词共有七种：
1)
从属连词：有whether，when，although，because，if等。
He will get the letter tomorrow if you send it off now. 如果你现在就把信发出，他明天就会收到。
I don’t know whether he will be able to come. 我不知道他明天是否能来。
2)
疑问代词：who，whom，whose，which，what。如：
Who he is doesn’t concern me. 他是谁与我无关。
We'd like to know what the young people want. 我们想知道年轻人想要什么。
3)疑问副词：when，where，why，how。如：
I asked how he was getting on. 我问他近况如何。
I can’t understand why they didn't come. 我不明白他们为什么没有来。
4)
关系代词：who，whom，whose，which，that。如：
Nobody who understands the subject would say such a thing. 懂得这一行的人是不会说这种话的。
Water that is impure often causes serious illness. 水不洁常会引起重病。
5)
关系副词：when，where，why。如：
July and August are the months when the weather is hot. 七八月是天气很热的月份。
She would like to live in a country where it never snows. 她喜欢住在不下雪的地区。
6)缩合连接代词：what，whatever，who，whoever，that，whichever。如：
Show me what you have written. 把你所写的东西给我看看。
Whoever does wrong is punished in the end. 恶有恶报。
7)缩合连接副词：whenever，where，when、why、how、wherever，however。如：
Whenever he goes out, he always takes his umbrella. 他每逢出门总是带伞。
Sit wherever you like. 你爱坐哪儿都成。
希望我能帮助你解疑释惑。