之所以称之为名词性从句，首先是因为其本质上具有名词的性质。名词可以充当主语、宾语、表语和同位语，那么由此推之，名词性从句也可以用在这四个位置上，于是由名词性从句这个干流中分出了四大支流:即主语从句、宾语从句、表语从句和同位语从句。

名词性从句靠关联词与主句连接起来，关联词充当着桥梁的作用。掌握关联词，也便掌握了从句的关键。

(一)主语从句

真题应用：

1.It is estimated that about 40 per cent of the world’s population use social media, and a large number of social media users look up to influences to decide what to buy. （20阅读）

2.It seems that your chances of winning and losing are about the same.(21阅读)

3. It is reported  5  less than 20% of these phones and up actually being recycled.（22选词）

4.What I hate most is to keep birds in cages.（22翻译）

5.It is said  3  rules of Weiqi can be learned in minutes. （23选词）

6.It is doubtful that safety is the real goal," said Jay Beeber,（24阅读）

主语从句在复合句中充当主语，大多数主语从句都可以用it作形式主语而把主语从句置于句尾。that引导主语从句时可用it作形式主语，that不可省；what引导的主语从句表示＂……的东西＂时，一般不用it作形式主语；whatever，whoever，whichever一般也不用it作形式主语。

1.主语从句的连接词总共有四类:

(1)由 that 引导的主语从句。that 在从句中不充当任何成分，本身也无实际意义，只起连接作用，可形象地比喻为“独木桥”。

如:That he will come is certain.

(2)由whether引导的主语从句。whether 在句中充当连接词，并且有其意义,故称之为“双道桥”。注意，从句中通常有or 或or not，这也是使用连接词 whether 的标志。

(3)由连接代词who(ever)、whom、whose、what 和which 引导的主语从句。连接代词在句中可充当句子成分，也有其意义，当然也有连接的作用，故称之为“三道桥”。如:

What you said is right.

(4)由连接副词 when、where、how 和 why 引导的主语从句。连接副词与连接代词一样，也具有三重作用，其充当的成分为状语。如:How the prisoner escaped is a mystery.

注意:有时为了求得句子的平衡，通常利用it作形式主语而将主语从句后置。如:

It's necessary that he return the book at once.

解题要诀:

如果从句中缺少主语、宾语、表语和定语，应选连接代词;从句缺状语时，应选连接副词;从中不缺少任何成分时，只能选that或whether,两者可以从句子的意思中判断。此规则也适用于表语从句、宾语从句和同位语从句。

2.常见的it替代that引导的主语从句的句式主要有以下几种：

(1)It＋系动词＋形容词(necessary，right，likely，unlikely，wrong，important，certain，clear，obvious，strange，normal等)＋that从句

It is certain that most of the farmers have brought in more money by all means.

(2)It＋be＋名词(短语)(a pity，a shame，good news，a fact，an honour，a wonder，no wonder等)＋that从句

It’s no wonder that you’ve achieved so much success.

(3)It＋be＋过去分词(said，told，heard，reported，decided，suggested，advised，ordered，remembered，thought，considered，well­known，announced等)＋that从句

It is said that the professor has already succeeded in carrying out the experiment.

(4)It＋特殊动词(seem，appear，happen，matter)＋that从句

It happened to me that I had been away when he called.

注意：(1)在＂It is necessary/important/strange/natural...＋that从句＂结构中，从句谓语常用＂(should＋)动词原形＂形式。

【拓展延伸】主语从句的引导词

【特别注意】当作主语的句子太长时，为保持句子平衡，常用it作形式主语，而将真正的主语置后。if＂是否＂，不可直接引导主语从句。

3.主语从句的特殊用法

（1）主语从句与定语从句的转换

What is needed has been bought.

All that is needed has been bought.  

所有需要的都被买了。

（2）几个特殊句型之间的转换

It is known to all that China has joined the WTO.

As is known to all, China has joined the WTO.

As we all know, China has joined the WTO.

众所周知，中国已加入WTO。

真题传送 

1.      leaves the room last should turn off the lights.(2005-44)

A.Anyone B. Whoever   C. The person D. Who

译：最后离开房间的人应该关灯。

解析:本题考查连接代词whoever的用法。whoever意为“任何一个人，无论谁”，可以引导主语从句。在本句中 whoever 既是从句 leaves the room last 的主格，又是should turn off the lights的主语。答案：B。

（二）表语从句

真题应用：

1.The problem with this approval is that at the end of a typical interview, the employers often don’t have a much better feel for the candidate than they do after reading the candidate’s resume. （20阅读）

2.中国古代的学者对竹子非常敬重，这也是为什么历史上有那么多以竹子为题的书画作品。（20翻译）

3.That's how we did it when I was a child ,...(21阅读)

4.That is when sleeping insects“wake up”.（23阅读）

5.She is also a traffic safety advocate for the nonprofit Creater Richmond Fit4Kids, which is why she owns a radar gun (雷达测速器).（24阅读）

6.“We’re maximizing our own interests, which is why we start to have a traffic jam at a given point.” says Nicola Pugno, a researcher at the University of Trento.（25阅读）

能引导主语从句的连词、连接代词、连接副词都可以引导表语从句，应用原则与主语从句相同。

表语从句只掌握以下三点便可:

（1）能引导主语从句的连词、连接代词和连接副词都能引导表语从句。

引导表语从句的连接词主要有：

连接词：that，whether

连接代词：who，whom，whose，which，what，whoever, whomever，whichever，whatever

连接副词：when，where，how，why

（2）连接词引导

The reason for his absence is that he hasn’t been informed.

他缺席的原因就是他没接到通知。

The question remains whether they will be able to help us.

问题还是他们能否帮我们。

（3）连接代词和连接副词引导

The problem is who will take charge of this shop. 问题是谁将接管这家店铺。

That is when I realized the importance of journalism. 那时我才意识到新闻工作的重要性。

注意：

1.as/as if/as though引导的表语从句常跟在特定动词后面，如seem，appear，look，taste，sound，feel等。

It sounds as if someone is knocking at the door. 听上去好像有人在敲门。

At that time, it seemed as though I couldn’t think of the right word. 当时我似乎怎么也想不出一个恰当的字眼来。

2.当主句的主语是the reason时，表语从句一般由that引导，这种用法常见于句型The reason why... is that...

The reason why he came late was that he got up late. 他来得晚是因为起床晚了。

真题传送

The reason Beethoven went away to the country is      he was gradually going deaf.(2012-45)

A. since B. that C. because D. as

解析:本题考查that引导的表语从句。系动词is 后面是一个完整的句子，不缺任何成分，只缺连接词。答案：B。

（三）宾语从句

真题应用：

1.Researchers have found that people who go to concerts, shows and museums, can live longer than____who do not.（20选词）

2.I must say that I always love birds, but there is a proper way of doing it.（22翻译）

3.Scientists who recorded humpback whale behavior in Australia discovered that fewer whales made the singing noises as their population grew.（23阅读）

4.It is clear she knows what it takes to get young people excited about science. （24阅读）

5.A 2014 study found that women between the ages of 20 and 40 who followed a six-week backward walking program lost body fat and improved their overall fitness.（25阅读）

6.Yet, I also realized that I was a part of this universe.（25翻译）

1.引导宾语从句的连接词主要有：

连接词：that，whether，if等

连接代词：what，who，whose，whatever，whichever，whoever等

连接副词：when，where，why，how等

（1）连接词that，whether，if引导

I think (that) you should turn to the teacher for help. 我认为你应该向老师寻求帮助。

I don’t know if/whether he still lives here after so many years. 我不知道这么多年后他是否还住在这儿。

注意：

whether/if都意为＂是否＂。一般情况下，它们可以互换，口语中常用if，但以下情况中，只能用whether。

1）与or not紧接连用时。

Let me know whether or not you can come. 请让我知道你是否能来。

2）作介词的宾语从句时。

We are interested in whether you will attend the meeting. 我们对你是否参加会议感兴趣。

（2）连接代词what，who，whose，whatever，whichever，whoever等引导

She asked me whose handwriting was the best in the class. 她问我班上谁的书法最好。

I’ll just say whatever comes into my mind. 我想到什么就说什么。

（3）连接副词when，where，why，how等引导

Do you know when the ancient Olympic Games began?

你知道古代的奥运会是什么时间开始的吗?

I’ve been thinking about how we can make the newspaper more interesting.

我一直在考虑如何使我们的报纸更用趣。

2. 宾语从句的语序

在宾语从句中要用陈述句语序。

He asked me when we could set out the next day. 他问我第二天什么时候可以出发。

Did you find out where she lost her car? 你查出她在哪里丢的车了吗?

3.宾语从句的时态

（1）当主句的谓语动词是一般现在时时，其宾语从句的时态可以是任何适当的时态。

She says (that) she works from Monday to Friday.

她说她周一至周五上班。(从句是一般现在时)

she says (that) she will leave a message on his desk.

她说她要在他桌子上留个便条。(从句是一般将来时)

She says (that) she has never been to Mount Emei.

她说她从来没有去过峨眉山。(从句是现在完成时)

（2）当主句的谓语动词是一般过去时时，其宾语从句的时态一般要用适当的过去时态。

He said there were no classes yesterday afternoon.

他说昨天下午没有课。(从句是一般过去时)

He said that he was going to take care of the baby.

他说他会去照看这个婴儿。(从句是过去将来时)

He said that they were having a meeting at that time.

他说他们那时正在开会。(从句是过去进行时)

（3）当宾语从句是表达客观真理和规律的句子时，其时态仍旧用一般现在时。

The teacher told us that nothing is difficult if we put our hearts into it.

老师告诉我们世上无难事，只怕有心人。

He said that light travels much faster than sound.

他说光比声音传播得快。

注意：在使用宾语从句时需要注意下面几点：

①动词find，feel，think，consider，make，believe，guess，suppose，assume等后有宾语补足语时，则需要用it作形式宾语，而将that宾语从句后置。

I think it necessary that we take plenty of boiled water every day.

我认为每天多喝开水是有必要的。

I have made it a rule that I keep diaries. 我每天写日记成了惯例。

②hate，like，take，owe，have，take for granted等表示＂喜欢；痛恨；认为＂的动词或动词短语和see to表示＂注意，留意＂后有宾语补足语时，需要用it作形式宾语而将宾语从句后置。

I hate it when they talk with their mouth full of food.

我讨厌他们满嘴食物说话。

When you start the engine, you must see to it that the car is in neutral.

启动发动机时，一定要使汽车的离合器处于空档位置。

③介词后的宾语从句。

She is always thinking of how she can do more for others.

她总想着如何才能为别人做得更多。

We are talking about whether we admit students into our club.

我们正在讨论是否让学生加入我们的俱乐部。

④宾语从句的否定转移。将think，believe，suppose，expect，fancy，imagine等动词后面宾语从句的否定词转移到主句中，即主句的谓语动词用否定式，而从句的谓语动词用肯定式。

I don’t think I know you. 我想我并不认识你。

I don’t believe he will come. 我相信他不会来。

真题传送

1. Because they usually receive the same score on examinations, there is disagreement as to             is the better student.(2008-30)

A. who       B. which      C. whom      D. whose

译：因为他们通常在考试中得到相同的分数，所以在谁是更好的学生这个问题上存在分歧。

解析:本题考查从句的引导词。本句意为:“因为他们通常在考试中得分一样，所以对于谁更优秀一些大家有不同的意见。”空格处为宾语从句的引导词，指代前文中的 they，并且在从句中作主语，因此应使用表示人称的who一词。答案：A。

2. A computer can only do__ you have instructed it to do.(2008-34)

A. how       B. after       C. what       D. when

译：计算机只能做你指示它做的事。

解析:本题考查宾语从句的引导词。宾语从句和其他名词性从句一样，在从句本身不缺失成分的情况使用引导词 that;在缺失成分的情况下，需要使用相应的代词或副词补足该成分。本题干中，从句本身缺少 do 的宾语，需要用表示物的 what 来表示。答案C。

3. Professor Lee's book will show you__ can be used in other context.(2011-41)

A. that you have observed B. how that you have observed

C. that how you have observed D. how what you have observed

译：李教授的书将向你展示如何将你所观察到的东西用于其他语境。

解析:本题考查宾语从句的引导词。宾语从句和其他名词性从句一样，在从句本身不缺失成分的情况，使用引导词 that;在缺失成分的情况下，需要使用相应的代词或副词补足该成分。本题干中，从句本身缺少状语，因此需要用how。第二考查点为主语从句，从句缺少宾语，所以用what 来引导。答案：D。

（四）同位语从句

真题应用

1.Evidence came up that specific speech sounds are recognized by babies as young as 6 months old. (2011单选)

2.All the while he was terrified by the fear that he had cancer of the stomach.(2014单选)

同位语从句跟在名词后面，进一步解释、说明该名词的具体内容。同位语从句常跟在名词idea, fact, news, hope, thought, suggestion等抽象名词之后，其连接词的范围和用法与主语从句相同。

1.用作同位语连词的 that 与用作定语从句关系词的that 有两点区别:

(1)同位语从句中的that只起连接作用，不能充当成分，而定语从句中的that可作从句成分。

(2)同位语从句是对前名词的解释和说明;而定语从句与所修饰的中心词之间是修饰与被修饰关系。

同位语从句的三种句型:

1.名词 that 陈述句

2.名词 定语 that 陈述句

The statement by the driver of the vehicle__ he did not see the lorry was rejected by the Court.

A. which B. that C. what D. how

答案:B。

3.名词 谓语 that 陈述句

An idea came to her_ she might do the experiment in another way.

A. which B. that C. what D. when

答案:B。

真题传送

1.All the while he was terrified by the fear      he had cancer of the stomach.(2014-36)

 A. which      B. that      C. what        D. such   

译：他一直害怕自己得了胃癌。

解析:本题考查同位语从句的引导词。先行词为fear，从句本身不缺失成分，故使用引导词 that。答案：B。

2.Evidence came up__ specific speech sounds are recognized by babies as young as 6 months old. (2011-47)

A. that         B. what        C. which       D. whose  

译：有证据表明，6个月大的婴儿就能识别特定的语音。

解析:本题考查同位语从句的引导词。先行词为evidence，从句本身不缺失成分，故使用引导词that，本题为分割结构，先行词和从句被谓语隔开。答案：A。

名词性从句知识清单:

一、that 引导名词性从句:

1.无具体意义，翻译不出来具体意思，一作用;

2.在从句中不作任何成分;

3.宾语从句中可省略，主语从句、表语从句、同位语从句中不可省略:

We all believe it true that Mr. Smith was elected chairman of the club.

宾语从句紧接在间接宾语之后：

He told me that he would put some signs on the envelope.

当一个动词带有两个或两个以上并列的that引导的宾语从句，第一个that可以省略，其余的that不可省略:

He said (that) the exhibition was excellent and that he wanted to visit it once more.

二、if/whether 引导的名词性从句:

1.有具体意思意义，翻译成“是否”，二作用;

2.不在从句中作任何成分;

3.不可省略;宾语从句中可以用whether, 也可以用if; 主语从句、表语从句、同位语从句中只能用whether

三、连接代词引导名词性从句:

1.有具体意义，三作用

2.不可省略

3.作从句中的成分，指人或物

what= whatever:物，作主、宾、表、定

who= whoever:人，作主

whom = whomever:人，作宾

which = whichever:人或物，作定

四、连接副词引导名词性从句:

1.有具体意义，三作用

2.不可省略

3.作状语，表时间、地点、方式、原因

when=whenever:表时间,

where=wherever:表地点

how:表方式

why:表原因