名词性从句

名词性从句

一．概述：在句子中起名词作用的各种从句统称为名词性从句。根据它们在句中的语法作用，这类从句又可分为主语从句、表语从句、宾语从句和同位语从句。二．名词性从句连接词

四．if, whether的区别

1.引导主语从句时，如果主语从句放在句首，只能用whether不能用if引导，但是如果用it 做形式主语，而把主语从句放在句末时，也可以用if引导.

2.引导宾语从句时常放在动词know, ask, care, wonder之后，if和whether均可。少数动词，如: leave, put, discuss, doubt后的宾语从句常用whether. 。

3.在介词后面的宾语从句中，在表语从句、同位语从句中，表“是否”，只能用whether；

4.whether和if都可以和or not连用,但是whether 之后可以直接跟or not,而if不可以。I do n’t know whether or not I will stay.（只能用whether）

5.在不定式前只能用whether.

如：I can’t decide whether to stay. 我不能决定是否留下。

五．与“命令、要求、建议”等相关的名词性从句中通常用虚拟语气，虚拟语气的构成是“should＋动词原形”或省去should，直接用动词原形。

六．名词性从句以考查引导词为主，同时考查时态，语序，与其它从句的区别以及混同虚拟语气的考查。

一．主语从句

1.主语从句定义：在复合句中充当主语的句子叫做主语从句。

That he will succeed is certain.

Whether wild life can be well protected is of great importance.

Who will go makes no different.

Which kind of food is the best is still not certain.

What is needed for the space trip is careful preparation.

Whoever comes is welcome.

How we can help the twins will be discussed at the meeting.

When they’ll start the project has not been decided yet.

Where he hid the money is to be found out.

Why dinosaurs died out remains a puzzle.

2.主语从句引导词按照在句中是否做成分主要分为三类：连词that、whether、if 连接代词、连接副词。

（1）由连词that引导的主语从句:引导词that无含义,在句中不做成分,引导主语从句的连词that 的省略：若that引导的主语从句直接位于句首，则that不能省略；若在句首使用了形式主语it，that引导的主语从句置后，则that 可以省略。

That you will win the medal seems unlikely.你想获得奖牌看起来是不可能的。That you are so indifferent bothers me.你如此冷淡使我很烦恼。

That she survived the accident is a miracle.她在事故中幸免于难简直是奇迹。

That you didn’t go to the talk was a pity. 很遗憾你没去听报告。(that不可省)

It was a pity (that) you didn’t go to the talk. 很遗憾你没去听报告。(that可省) （2）由连词whether 引导的主语从句：whether有含义“是否”，在句中不做成分，不可以省。whether 可以和or not连用。

Whether it will do us harm remains to be seen. 是否对我们有害还要看一看。Whether they would support us was a problem.他们是否会支持我们还是一个问题。Whether she is coming or not doesn’t matter too much.她来不来都无关紧要。

（3）如果主语从句放在句首，不能用if引导，但是如果用it 做形式主语，而把主语从句放在句末时，也可以用if引导.

Whether Mary really heard him is really doubtful.（对）

It was doubtful if Mary really heard him.（对）

If Mary really heard him is really doubtful.（错）

（4）连接代词引导的主语从句：连接代词who, whose, whom, which, what, whoever, whomever, whichever, whatever，在句子起名词性作用，担当一定成分。不能省略。

Who killed the scientist remains a question.

Whom she borrowed money from still puzzled him.

Which side will win is not clear.

What you need is more practice.你所需要的是更多的训练。

What I want to know is this. 我想知道的就是这事。

Whatever he did is right.

Whoever breaks the law will be punished. (主语从句)

= Anyone who breaks the law will be punished. (定语从句)

比较：Whoever breaks the law，he should be punished.(让步状语从句)

= No matter who breaks the law，he should be punished. (让步状语从句)

（4）用连接副词when, where, why, how引导的名词性从句(其连接副词有含义,在句中作状语。)

Where we should leave it is a problem.

When they will come hasn’t been made pubic.他们什么时候来还不知道。

How it was done was a mystery. 这是怎样做的是一个谜。

3.主语从句注意事项

（1）为了避免主语冗长,句子头重脚轻,经常用it 做形式主语,而将主语从句置后（尤其是当谓语较短时）。

①That light travels in straight lines is known to all.光沿直线传播，这是众所周知的事。

=It is known to all that light travels in straight lines.众所周知光沿直线传播。

②Whether they would support us was a problem. 他们是否会支持我们还是一个问题。

=It was a problem whether they would support us.

③When the plane is to take off has not been announced.飞机何时起飞还没有宣布。= It has not been announced when the plane is to take off.还没有宣布飞机何时起飞。（2）如果句子是疑问句，则必须用带形式主语it的结构

Has it been settled who will be sent to carry out the task?

谁将被派去执行这项任务决定了吗？

（3）连接代词What引导的名词性从句

①what引导主语从句时，常常翻译为“所…….的”或“…..的事物/东西/人/样子/地方等”此时无疑问含义。What在从句中作主语，宾语。

What you need is a good-sized canvas bag.