名词性从句
1. 概念 在句子中起名词作用的句子叫名词性从句。名词性从句的功能相当于名词词组,它在复合句中能担任主语、宾语、表语、同位语、介词宾语等, 因此根据它在句中不同的语法功能,名词从句又可分别称为主语从句、宾语从句、表语从句和同位语从句。 Who will win the match is still unknown.
I want to know what he has told you.
The fact is that we have lost the game.
The news that we won the game is exciting.
2. 引导名词性从句的连接词可分为三类:
连接词/从属连词that, whether, if 不充当从句的任何成分
连接代词: what, whatever, who, whoever, whom, whose, which.
连接副词: when, where, how, why
3. 不可省略的连词： 引导主语从句、表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.
What I want to tell you is that he will come back soon.
主语从句的用法注意:
连词that, whether在从句中不担任 句子成分,只起连接作用,不能省略 (注: if不可用来引导主语从句）
it 作形式主语和it引导强调句的比较
it 作形式主语代替主语从句,主要是为了平衡句子结构, 主语从句的连接词有变化。而it引导的强调句则是对句子某一部分进行强调,无论强调的是什么成分,都可用连词that。被强调部分指人是也可用who/whom。
例如: It is a pity that you didn’t go to see the film.
It doesn’t interest me whether you succeed or not.
It is in the morning that the murder took place.
It is John that broke the window.
宾语从句的用法
关联词只能用 whether或if, 不能用that的情况如下： 若doubt一词作"怀疑”解接宾语从句时, 主句为肯定句用whether或if, 主句为否定句或疑问句用that。如： I doubt whether he will come soon.
I do not doubt that he will come soon.
Do you doubt that he will come soon？
时态： 如果主句是过去的时态(包括一般过去时, 过去进行时), 那么从句的时态一定要用相对应的过去的某种时态。
When will Professor Li give us a talk?
We wanted to know … Jim is a good student.
The teacher said … Has Mr. Green been in Beijing for five years? He asked …
在think, believe, suppose, expect 等动词之后,宾语从句中谓语的否定常转移到主句的谓语上。
I don’t think he will see you.
I don’t believe he will go.
We don’t expect he is coming.
I don’t think he can do it, can he?
在suggest, insist, demand, order, require 等表示建议,命令,要求的动词后,从句的谓语动词要用虚拟语气。如: I insisted that he（should）do it at once.
She suggested that the work (should) be finished at once.
注意:
1. 当从句是客观真理,定义,公理,定理时用一般现在时。
2. 如果主句的谓语动词是ask时,连词不可能是that;如果主句的谓语动词是say时, 连词用that。
1) She says (that) she will leave a message on his desk.
2) He asks if I like playing the piano .
在接复合宾语的句子中, 为了保持句子平衡, 用it 作形式宾语,将从句放于句尾, 常接复合宾语的动词有: make, find, see, hear, feel, think...
I think it necessary that we take plenty of hot water every day.
I think it a pity to waste the food.
表语从句的用法注意:
在表语从句中,当reason做主语时, 引导词只能用that,不能用because,
如:他迟到的原因是因为他没有赶上早班车。
The reason why he was late was that he didn’t catch the early bus.
主句的主语是名词idea, advice, suggestion, order, request, requirement时, 表语从句应用虚拟语气,即: (should) +v.
My suggestion is that we should have a discussion about this matter instead of just setting it aside.
同位语从句
同位语从句一般跟在名词fact, news, promise, truth, belief, thought, idea, answer, information, knowledge, doubt, hope, law, opinion, plan, suggestion后面, 用以说明或解释前面的名词.
The news that our team has won the match is true.
His delay is due to the fact that the car went wrong halfway.
注: 1. that 引导同位语从句与that 引导定语从句的区别:
引导同位语从句的that 无实际意义, 不作从句的任何成分, 但不能省略，，
而引导定语从句的that 从句的某个成分，在从句中作宾语时可以省略。
He told me the news that our team won the match.
He told me the news that was very exciting.
We are interested in the news that some foreigners would visit our school.
We are interested in the news that he told us.
2. 在have no idea 之后常用wh-引导同位语从句.
I have no idea where he has gone.
I have no idea when he did it. I have no idea what he did.
| 
