三大从句语法

从句可分为三类:即名词性从句、形容词性从句（即定语从句）和副词性从(即状语从句）。

引导从句的词称作关联句。

一、名词性从句
引导这些名词性从句的关联词包括：从属连词：that，if, whether连接代词：who, whoever whom, whomever ，which ,whichever ，what ,whatever ，whose 连接副词where, when, why, how。

其中, 从属连词只起连接作用，在从句中不充当任何句法成分，而连接代词和连接副词既起连接作用, 在从句中又充当一定的成分。

不可省略的连词：1. 介词后的连词2。

引导主语从句和同位语从句的连词不可省略。

That she was chosen made us very happy。

We heard the news that our team had won。

比较：whether与if 均为"是否"的意思。

但在下列情况下，whether 不能被if 取代:1。

whether 引导主语从句并在句首2。

引导表语从句 3. whether从句作介词宾语4. 从句后有"or not” 例：Whether he will come is not clear。

The fact is that he didn't go to the dinner party。

I don't know if he will attend the meeting。

1. 在含有主语从句的复合句中，为保持句子平衡, 常用it作形式主语,而将真正的主语从句置于句末。

That—从句作主语通常用it作先行词，而将that—从句置于句末，例如：
It is quite clear that the whole project is doomed to failure。

很清楚，整个计划注定要失败。

It’s a pity that you should have to leave.你非走不可真是件憾事.
用it作形式主语的that—从句有以下四种不同的搭配关系:
A It + be +形容词+ that—从句例:It is necessary that…有必要……It is important that…重要的是……It is obvious that… 很明显……
B. It + be + —ed 分词+ that-从句例如：It is believed that…人们相信……It is known to all that…从所周知……It has been decided that… 已决定……
C。

It + be +名词+ that—从句例:It is common knowledge that………是常识It is a surprise that… 令人惊奇的是……It is a fact that… 事实是……
D. It +不及物动词+ that—分句例：It appears that…似乎……It happens that…碰巧……It occurred to me that… 我突然想起……
2. 为保持句子平衡，that引导的宾语从句也常用it代替，而将真正的宾语从句置于主句句末。

这常常出现在主句有形容词或分词作宾语补足语的情况下。

He made it quite clear that he preferred to live here。

3. 从属连词whether和if都作“是否…"解, 但if不可引导主语从句和表语从句。

whether可与or(not）连用, 而if不可以. I don't know whether (if）she is at home.
Whether she comes or not makes no difference。

4。

that和what引导名词性从句的区别：that在从句中不充当成分,而what在从句中充当一定的成分, 如主语、表语、宾语等.that可省略, what则不可省.
He always means what he says. She suggested (that) he do it at once.
5. 同位语从句大多由从属连词that引导，常跟在下列名词后面，如fact, idea，opinion，news，hope，belief等，that不可省。

同位语从句一般用来解释说明这些名词的具体含义和内容。

We are familiar with the idea that all matter consists of atoms.
The news that we are invited to the conference is very encouraging.
二、形容词性从句
引导定语从句的关联词包括：(1)关系代词：that，which, whose, who, whom，as; (2）关系副词:when，where，why.
关系代词和关系副词在定语从句中都充当一定的句法成分,关系代词在句中充当动词的宾语
时，一般可省去。

关系代词的选用比较复杂，它受下列条件的制约: (1）先行词是指人还是指物(2）关系代词在从句中的句法功能(3）定语从句是限定性的还是非限定性的。

关系代词的选用情况见下表：
先行词在从句中的句法功能用于限定性或非限定性定语从句只用于限定性定语从句
指人或指物指人指物
主语who which that
宾语whom which that
定语whose whose(of which)
I know that he is a man who （that) means what be says.
The gentleman whom （that) she met addressed her with courtesy(礼貌).
The watch which （that) was lost has been found。

Here is the meterial which （that) you need.
You're the only one whose advice he might listen to.
关系副词的选用相对来说较简单。

如先行词为表示时间的名词，如time, day等，则用when; 如先行词为表示地点的名词，如place, house，area等,则用where；如先行词为reason，则用why。

例：I'll never forget the mountain village where (in which）I spent my childhood.
I don’t know the reason why (for which）he did that.
1。

当先行词是all，something，nothing等不定代词时;或先行词前有first，last, only，few，much, some，any, no等修饰时；或先行词前有形容词最高级修时，一般只用that而不用which来引导定语从句。

例：I’ve explained everything （that) I can to you。

This is the most beautiful compus （that）I've ever been to。

2. 定语从句分为限定性定语从句和非限定性定语从句，限定性定语从句与主句关系紧密, 为句中不可缺少的部分，如去掉, 主句意思不完整。

非限定性定语从句与主句关系松散，如去掉, 主句内容仍完整。

在书面语中, 非限定性定语从句一般被逗句隔开。

非限定性定语从句一般不用that引导。

引导非限定性定语从句的关系词不可省略。

His speech, which bored everyone, went on and on.
The general’s daughter, whose name is Ann，gave me a sweet smile.
3. 先行词也可以是整个句子.这时, 一般用which或as来引导定语从句。

which在从句中可充当主语、宾语等, as在从句中一般只充当主语。

which与as引导此类定语从句的区别在于：which只能置于句中或句末, 而as的位置比较灵活, 可置于句中、句末, 又可置于句首。

Water consists of hydrogen and oxygen，which (as）is known to all。

As had been expected，he finished first in decathlon（十项全能) at that Olympic Games。

4。

关系代词在定语从句中有时也做介词的宾语。

如果介词被置于关系代词前, 一般只用介词+which或介词+whom, 而不用介词+that来此导定语从句。

如果介词被置于从句句末, 则可用that代替which或whom,且that这时可省去.
This is the ring on which she spent 1，000 dollars.
One of my colleagues whom (that) you are familiar with will come today.
区分关系代词与关系副词方法一：用关系代词，还是关系副词完全取决于从句中的谓语动词。

及物动词后面无宾语，就必须要求用关系代词；而不及物动词则要求用关系副词。

例如：This is the mountain village where I stayed last year.
I’ll never forget the days when I worked together with you。

方法二：准确判断先行词在定语从句中的成分(主、谓、宾、定、状），也能正确选择出关系代词/关系副词。

例1. Is this museum _D__ you visited a few days age?
A。

where B. that C. on which D。

the one 例2. Is this the museum __A__ the
exhibition was held .A. where B。

that C. on which D。

the one
三、副词性从句
在复合句中, 起状语作用的从句称作状语从句。

状语从句分为:时间状语从句、地点状语从句、条件状误从句、原因状语从句、让步状语从句、比较状语从句、目的状语从句、结果状语从句、方式状语从句。

状语从句可放在句首或句末.如状语从句位于主语前,一般用逗号将其与主句隔开。

（一)时间状语从句
When you cross a main road，you must be very careful.
Until we learn the facts，we can’t do anything about it。

注1。

when，as，while引导时间状语从句时都可以表示主句的动作与从句的动作同时发生，即同时性。

它们的区别在于：when和as引导的状语从句中的动作既可以是延续性的，也可以是非延续性的，即瞬时性的；while引导的状语从句中的动作只能是延续的动作或状态.
当主句和从句中的动作均为延续动作时, 一般用while, 而不用when或as。

当表示两个同时发展、变化的情况时，一般用as，作“随着…”解。

When she comes，I shall tell her to wait for you. As she got older, she got wiser.
While Peter was reading，his wife was cooking。

2。

有些副词和一些表示时间的名词词组也可用作从属连词，引导时间状语从句。

如instantly，immediately，directly，the day, every time, the minute，the second, the moment 等。

Immediately he arrived, he started describing us what had happened.
The day he returned home, his grandpa was alrady dead.
（二)条件状语从句
引导条件状语从句的从属连词有：if，unless, as (so) long as, only if（只要)。

If you don't come on time，we'll start out without you.
As (so）long as you keep on trying，you'll certainly succeed。

注:除了以上提到的从属连词外，还有其它的一些词或词组也可引导条件状语从句。

如：providing that，provided,，supposing that，，suppose that,，on condition that,，in case 等。

I will go providing that my expenses are paid。

要是我的费用有人代付我就去
Supposing he is not at home，what then？假如他不在家，那怎么办?
You can use the bicycle on condition that you return it tomorrow。

只要你明天归还,自行车你可以拿去用.
In case she comes back，let me know immediately。

假使她回来了,立刻告诉我
Take the raincoat in case it rains.带着雨衣,以防下雨。

（三)原因状语从句
引导原因状语从句从句的从属连词有:becasue, since，as, now（that），in that, considering that 等。

Considering he’s only been learning English a year he speaks it very well。

考虑到他只学了一年英语，他讲得算是很流利了。

We didn’t know what to do as we were just visiting there。

我们不知道该怎么办，因为当时我们仅仅在那里作访问。

Since it is so hot，let's go swimming。

既然天气这么热,我们去游泳吧。

注：in that和now（that）的用法: in that引导的从句对主句进行解释和说明，意思是：在…
方面, 在于…；因为。

now（that)表示既然。

Theory is valuable in that it can provide a direction for practice.理论所以有价值,就在于它能给实践指出方向。

Now (that）the weather has improved, let's go out for a picnic.既然天气已转好，我们就出去野餐吧.
(四）让步状语从句
引导让步状语从句的从属连词有：though, although, even if (even though)，as, no matter…despite the fact that，in spite of the fact that, while。

Tired as he was，he sat up late。

他虽然疲倦,可仍然很晚才睡。

No matter how they slander us, we will never give in.不管他们怎样诽谤我们，我们决不让步。

While I like the color of the hat, I do not like its shape.虽然我喜欢这顶帽子的颜色,但我不喜欢它的形状。

注：一些疑问词在词尾加上ever后, 也可引导让步状语从句,相当于no matter+疑问词。

这些词包括: whatever, wherever，whenever, whoever，however。

Whatever he says, don't beleve him.不管他说什么都不要想相信他。

Whoever you are, you must obey the traffic regulations。

(五）目的状语从句
引导目的状语从句的从属连词有：so that, in order that，lest，in case, for fear that。

They climbed to the top of the building in order that they could get a bird’s—eye view of the city. Ask her to hurry up with these letters so that I can sign them.
Take an umbrella in case it rains。

We dare not play jokes on him lest he should become angry。

我们不敢开他玩笑生怕他动气。

注:so that和in order that的区别：so that更常用，in order that更正式.so that引导的从句一般置于句末，而in order that引导的从句既可置于句首, 又可置于句末。

In order that the grass and flowers could bloom again,it was necessary that the rocks should be removed。

She got up early so that she could catch the first bus.
（六）结果状语从句
结果状语从句一般由下列连词引导: so that，so…that, such…that。

He overslept，（so) that he was late for work。

They got such a fright that they dropped the bag and ran away。

注：1。

so…that和such…that的区别。

so后接形容词或副词, such后接名词。

It was so cold that we had to cancel the game。

It’s such a good chance that we mustn’t miss it。

2。

so that既可引导目的状语从句，也可引导结果状语从句.so that引导目的状语从句时, 一般从句动词前会出现can（could),may(might）,shall(should),而so that引导的结果状语从句表示客观事实，不会出现上述词语。

引导结果状语从句的so that前常有逗号，表示强调。

so that引导的目的状语可置于句首,而so that引导的结果状语从句只能置于句末。

He left early so that he could catch the train。

他早早动身，以便能赶上车.(目的）
He left early，so that he caught the train.他早早动身, 赶上了火车。

(结果）
（七)方式状语从句
引导方式状语从句的从属连词有as, as if(though），the way, how。

He made some changes as you had suggested.
She was behaving as if （though) she hadn't grown up.。