1. 主从复合句的概念：

即上一章所提的由两个或两个以上的分句构成一个复杂句，其中一个为主句，其余的分句为主句的成分。

2. 主句和从句的逻辑关系分类：

1) 从句作主句的定语(修饰主句中的一个名词短语或代词)，这种从句叫定语从句。具体见下节。

2) 从句做主句的状语。这种从句叫状语从句。

3) 从句象一个名词结构一样，在从句中作主语、宾语、表语、同位语，这种从句叫名词性从句。

3. 从句的结构：

所有从句)的结构都是这个模式：连词(或称从句引导词，单纯只起连接作用或兼作从句成分)+主语部分+谓语部分。

4. 定语从句

1) 定语从句的概念：跟在一个名词短语或代词后面，修饰该名词短语或代词的一个分句。被修饰的名词短语或代词叫先行词。如下列例句中的____部分为主句，黑斜体部分为先行词，　　部分为定语从句部分：

Justin’s mother, who was working that night, was surprised that his son did not tell anyone that he was staying out late.

Standing inside were lots of white-skinned strange-looking creatures which had large black eyes.

2) 定语从句引导词：

在定语从句中，从句引导词既连接从句和主句又作从句的成分。共分为三类

(1) 关系代词，在定语从句中指代先行词，作定语从句的主语、宾语或表语。包括：

① 指代人 (也就是引导修饰人的定语从句) 的关系代词who, whom, that，其中who和that既可以作主语也可以做宾语，whom只可以作宾语。作表语只用that。如：

The police officer who / that had ruled out the possibility of murder was very experienced.(who / that作定语从句的主语)

The boy who(m) 91eXaM.org/ that they found missing was called Justin Foster.(who / whom / that作定语从句的谓语动词found的宾语)

Tom is not the small boy that he used to be. (that在从句中作表语)

② 指代事物(也就是引导修饰事物的定语从句) 的关系代词which和that，两者都既可以作主语也可以做宾语。That还可作表语。如：

The spaceship that / which moved around to the side of the house gave off very bright lights.(that / which作定语从句的主语)

Water, without which humans couldn’t live, is the most valuable resouce on the earth.(which作定语从句中的介词without的宾语)

This place is not the village that it was ten years ago.(that在从句中作表语)

(2) 关系限定词whose，在定语从句中作定语，指代“名词先行词’s”或物主限定词his, her等，引导修饰人(间或为事物，此时可用whose可被of which替代)的定语从句。如：

The strange-looking man whose eyes were large and black walked over to Justin.(whose作eyes的定语，指代the strange-looking man’s，从句修饰人)

The house whose windows we have just fixed were broken into by burglars.(whose作 windows的定语，指代the house’s，从句修饰事物)

(3) 关系副词where, when和why，在定语从句中作状语，相当于“介词+地点名词先行词/时间名词先行词/原因名词先行词”，各自引导修饰这些名词的定语从句。如：

The mountain where the volcano lies is not far from here.(where在从句中作谓语动词lies的状语，相当于in the mountain从句修饰the mountain)

The days when people felt content with a simple life are forever gone.(when在从句中作谓语动词felt的状语，相当于in the days，从句修饰the days)

He gave us no reason why he took the job.(why在从句中作谓语动词took的状语，相当于for the reason，从句修饰reason)

4) 介词+定语从句引导词which / whom：

当定语从句引导词作介词的宾语时，可以将介词提到引导词前，以强调介词和引导词的介宾关系;介词+which / whom在从句中作状语或定语;有些情况下，介词+which相当于where / when / why。如：

The man with whom you talked is an expert in earthquakes.(with whom在从句中作状语修饰谓语动词talked)

That’s the gate at which the young woman was picked up by some strangers.(at which=where, 在从句中作状语修饰谓语动词was picked up)

The day on which Nelson Mandela helped me was one of my happiest.(on which=when，在从句中作状语修饰谓语动词helped)

I can’t tell you the reason for which she insists on doing that.(for which=why，在从句中作状语修饰谓语动词insists)

The shelters took in thousands of flood survivors, many of whom / of whom many suffered from malaria.(of whom在从句中作定语修饰many)

The house of which the windows / the windows of which are open was broken into by burglars. (of which在从句中修饰定语the windows) = The house whose windows are open was broken…

5) 定语从句的分类：

(1) 限定定语从句：

起着界定先行词的身份，而不至与同类人或事物混淆的定语从句，一般不用逗号和主句隔开。如：

One of my brothers who is in the army now used to be an art student. 我一个现在当兵的兄弟学过艺术。(定语从句界定one of my brothers的身份：有多个兄弟，这里指的是当兵的兄弟)

The travellers who had already been informed about the flood stopped their journey. 那些已经获悉洪灾的路人暂停了行程。(只有获悉洪灾的路人才终止了行程，没有获悉洪灾的路人并没有暂停其行程。)

(2) 非限定定语从句：

不起界定先行词的身份作用，因为先行词身份已经为读者或听话人所确定而不会混淆(要么由于同类只有其一个，或者上下文已经让读者或听话人明确其身份)，而是起着给先行词增加信息的作用。一般要用逗号和主句隔开。不能用that引导非限定定语从句。

My brother, who is in the army now, used to be an artist. 我兄弟学过艺术，他现在当兵。(只有一个兄弟)

The travellers, who had already been informed about the flood, stopped their journey. 由于路人们已经获悉了洪灾，他们都暂停了行程。(所有的路人们都终止了其行程，用从句顺便说明一下其原因)

6) that和which / who的适用范围：

两者都可以引导修饰事物的定语从句，但如下情况多用that：

(1) 先行词是表物不定代词all,few,little,much,something,nothing,anything等。如：All that we have to do is to practise every day.

(2) 先行词被序数词或形容词最高级所修饰。如：The first lesson that I learned will never be forgotten.This is the best film I've ever seen.

(3) 先行词被all, any, every, each, few, little, no, some等修饰。如：I have read all the books(that)you gave me.

(4) 先行词被the only, the very, the same, the last修饰。如：He is the only person that/(who) I want to talk to.

(5) 先行词包括人和物。如：They talked of things and persons that they remembered.

(6) 当句中已有who时，为避免重复。 如：Who is the man that is talking to John?

(7) 用作关系代词，修饰表示时间的名词如day, time, moment等，代替when。如：It happened on the day that/when I was born.

7) as, which 引导非限定性定语从句

由as, which 引导的非限定性定语从句，as和which可代整个主句(即先行词是整个主句)，相当于and this(as还带有“正如”含义)。As从句可置于主句前后中，which在主句后。如：

As we know, smoking is harmful to one's health.= Smoking, as we know, is harmful to one’s health. = Smoking is harmful to one’s health, as we know.

The sun heats the earth, which is very important to us.

8) as在固定搭配中引导定语从句

在the same…as…和such…as…中as也可以引导定语从句，不能换成别的引导词。如：

I have got into the same trouble as he was in. 我现在的麻烦和他以前的一样。(as在从句中作in的宾语)

He is sucn an asshole as would beat you for nothing. 他混球得狠，没事给你一顿揍。(as在从句中作从句的主语)

9) 定语从句引导词的省略：

(1) 引导词作宾语时在限定性从句中可以省略，但介词+which / whom中不能省略which / whom。

(2) Way(方法/方式)的定语从句表示“某人做某事/某事被做(的方法)”时候，可以省略in which 或that.。如：

I don’t like the way (that / in which )you speak to your father.

10) 选择引导词的原则：

看定语从句还需要什么成分，如果缺主宾表，就用来源:91考试网 www.91eXam.org关系代词，再根据以下情况确定是哪个具体的关系代词：修饰物或人;作主或宾还是表语;限定或非限定;特殊规定或搭配。

如果从句不缺少主宾表，此时句子看上去很健全，那只能添加枝叶成分状语，则用关系副词，再根据是修饰时间、地点还是原因的先行词确定具体的关系副词。