根据从句语法功能的不同可分为:   1：名词性从句： ①主语从句：用作主语的从句，关联词有从属连词、疑问代词、疑问副词、缩合连接代词、缩合连接副词等。  

That he finished writing the composition in such a short time surprised us all.

Whether we will go for an outing tomorrow remains unknown.

    ②表语从句：用作表语的从句，关联词与引导主语从句的关联词很多都一样。有:that, what, who, when, where, which, why, whether, how, whoever，whomever，whichever ，whatever等。还有如because, as if, though等。

  He has become a teacher.   他已经成为一名教师。

  He has become what he wanted to be ten years ago.   他已经成为了他10 年前想成为的职业。

  ③宾语从句:在句子中起宾语作用的从句,宾语从句分为三类:动词的宾语从句、介词的宾语从句和形容词的宾语从句。

A 、作动词的宾语:  

e.g.I heard the news.   I (主语) heard (谓语动词) the news.名词作宾语  

I (主语) heard (谓语动词) that he would come here later on.一个句子作宾语---宾语从句  

B 、作介词的宾语:   e.g.He said nothing about the plan.  

He (主语) said (谓语动词) nothing (代词作动词的宾语) about (介词) the plan. 名词作介词的宾语  

C、 做有动词意义的形容词的宾语  

e.g.I'm afraid that I can't win.

④同位语从句:它的作用相当于名词，对前面的名词(短语)加以补充说明或进一步解释，相当于一个表语从句，它们之间的关系就是同位关系，即主表关系。其关联词多为that。 I heard the news that our team had won.   我听到了我们队获胜的消息。

  I had no idea that you were here.   我不知道你在这里。

    2：形容词性从句： 定语从句:其作用是作定语修饰主句的某个名词性成分，

①引导定语从句的关联词有who,whom,whose,that,when,where,why 和 which. 在非限制定语从句中，只可用which,who,whose,where,when.,如果指代前面整个句子，多用which.

Those who are in favor of the proposal are expected to discuss it in detail after the meeting. (有人认为那些对这个提案有兴趣的人最好是在会后再具体讨论它。)  

There are many organizations whose purpose is to help the homeless. (存在着许多旨在帮助无家可归者的组织。)  

② 当引导定语从句的先行词前有all,any,no,little,much,very first等词，或先行词前为形容词最高级所修饰时，或先行词为all,anything,nothing,something,everything时，从句的引导词只能用that.  

The only thing that matters to the children is how soon they can have their holiday. (孩子们唯一关心的是他们什么时候放假?)

  These are the very points that puzzle me. (真正困扰我的是这些观点。)

③as 可做引导词引导定语从句，多和such,the same 连用. As 引导的定语从句也可修饰整个句子，既可放在先行词后，也可放在句子开头.

  例句:   Such people as you describe are rare nowadays.(你描述的那一类人现在很少了。)

④介词+which/whom/whose从句  

The driver is the man from whose room she had stolen the gold watch.(她就是从那个司机的房间偷了金表的。) ⑤代/名+介词+which 从句  

He is needing a book,the name of which I don't know.