名词性从句
在句子中起名词作用的句子叫名词性从句(Noun Claus）。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。
第一节知识点讲解
顾名思义，主语从句在句子中作主语。有时本身出现在主语的位置上，也有时出于句子结构的考虑退到句子的尾部，前面用形式主语it代替。从句作主语时，谓语动词一般为单数形式。如:
What I saw was beyond any verbal description.
That his hair was turning grey worried him a bit.
我真高兴作文Why the company denied the contract is still unknown.
When and where the government will build a city square is under discussion.
It is pretty annoying that a small part of the machine is missing.
It remains to be en whether the new novel will be well received.
Tips: 主语从句的that绝对不能省去。因为句子是不能做主语的，故用that引导。若去掉则没有了主语，而宾语从句的that可省。色人阁五月天
主语从句：That he is right is known to all of us.
宾语从句：We all know (that) he is right.
1. It 作形式主语和it引导强调句的比较过年作文200字
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It 作形式主语代替主语从句，主要是为了平衡句子结构，主语从句的连接词没有变化。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。被强调部分指人时也可用who/whom。例如：
a) It is a pity that you didn’t go to e the film. 你不去看那场电影真可惜。
b) It doesn’t interest me whether you succeed or not. 我对你成功与否不感兴趣。
c) It is in the morning that the murder took place. 谋杀案是在早上发生的。（强调句型）
d) It is John that broke the window. 是John打碎的窗户。（强调句型）
2. 用it 作形式主语的结构
(1) It is ＋名词＋从句
It is a fact that … 事实是…
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It is an honor that …非常荣幸
It is common knowled ge that …是常识
(2) It is ＋形容词＋从句
It is natural that… 很自然…
It is strange that… 奇怪的是…
(3) It is ＋不及物动词＋从句
It ems that… 似乎…
It hap pened that… 碰巧…
It appears that… 似乎…
(4) It ＋过去分词＋从句
It is reported that… 据报道…
It has been proved that… 已证实…
It is said that… 据说…
3. 主语从句不可位于句首的五种情况：
（1）if 引导的主语从句不可居于复合句句首。
（2）It is said /reported…结构中的主语从句不可提前。例如：
正确表达：It is said that President Jiang will visit our school next week.
错误表达：That President Jiang will visit our school next week is said.
（3）It happens/occurs…结构中的主语从句不可提前。例如：
正确表达：It occurred to him that he failed in the examination.
错误表达：That he failed in the examination occurred to him.
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（4）It doesn’t matter how/whether …结构中的主语从句不可提前。例如：
正确表达：It doesn’t matter whether he is wrong or not.
错误表达：Whether he is wrong or not doesn’t matter.
（5）含主语从句的复合句是疑问句时，主语从句不可提前。例如：
正确表达：Is it likely that it will rain in the evening?
错误表达：Is that will rain in the evening likely?
4. what 与that 在引导主语从句时的区别
what 引导主语从句时在句时在从句中充当句子成分，如主语．宾语．表语，而that 则不然。例如：
a) What you said yesterday is right.
b) That she is still alive is a consolation
宾语从句就是在复合句中作宾语的名词性从句，通常放在主句谓语动词(及物动词) 或介词之后。
We assumed that there would be more than 100 guests.
He told the police in detail what he saw and heard.茶馆装修设计
Nobody is sure what humans will look like in a million years.
That will depend on whether they can get the chance.
Whether I will have the time I am not sure at the moment.
The conductor complained that we were not gifted in singing and that he would never come again.
1. 作动词的宾语
(1) 由that引导的宾语从句(that 通常可以省略), 例如：
I heard that be joined the army. 我听说他参军了。
(2) 由what, whether (if) 引导的宾语从句，例如：
a) She did not know what had happened. 她不知道发生了什么。
b) I wonder whether you can change this note for me. 我想知道你是否能帮我改一下笔记。
(3) 动词＋间接宾语＋宾语从句。例如：
She told me that she would accept my invitation. 她对我说她会接受我的邀请。
2. 作介词的宾语，例如：
Our success depends upon how well we can cooperate with one another. 我们的成功取决于我们之间的合作。
3. 作形容词的宾语，例如：
I am afraid(that) I’ve made a mistake. 我恐怕我已经犯了一个错误。
注意：that 引导的从句常跟在下列形容词后作宾语：anxious, aware, certain, confident, convinced, determined, glad, proud, surprid, worried, sorry, thankful, ashamed, disappointed, annoyed, plead, hurt, satisfied, content 等。也可以将此类词后的that 从句的看作原因状语从句。
4. it 可以作为形式宾语
it 不仅可以作为形式主语，还可以作为形式宾语而真正的宾语that 从句则放在句尾，特别是在带复合宾语的句子中。例如：
We heard it that she would get married next month. 我听说她下个朋就会结婚了。
5. 后边不能直接跟that 从句的动词
这类动词有allow, refu, let, like, cau, force, admire, condemn, celebrate, dislike, love, help, take, forgive等。这类词后可以用不定式或动名词作宾语，但不可以用that引导的宾语从句。如：
正确表达：I admire their winning the match.
错误表达：I admire that they won the match.
6. 不可用that从句作直接宾语的动词
有些动词不可用于“动词＋间接宾语＋that从句“结构中，常见的有envy, order(命令), accu, refu, impress, forgive, blame, denounce（公开指责）, advi, congratulate等。例如：
正确表达：He impresd the manager as an honest man.
错误表达：He impresd the manager that he was an honest man.
7. 否定的转移
若主句谓语动词为think, consider, suppo, believe, expect, fancy（想象）, guess, imagine等，其后
的宾语从句若含有否定意义，一般要把否定词转移到主句谓语上，从句谓语用肯定式。例如：
I don’t think this dress fits you well. 我认为这件衣服不适合你穿。
三．【表语从句】
表语从句在复合句中作表语的名词性从句，放在系动词之后，一般结构是“主语＋连系动词＋表语从句”。可以接表语从句的连系动词有be, look, remain（留下、保持、依然）, em等。引导表语从句的that常可省略。另外，常用的还有the reason is that… 和It is becau 等结构。例如：
1) The question is whether we can make good preparation in such a short time.
2) This is why we can’t get the support of the people.
3) But the fact remains that we are behind the other class.
4) The reason he is late for school is that he misd the early bus.
同位语从句就是在复合句中作名词的同位语的名词性从句。
1. 同位语从句的功能
同位语从句对于名词进一步解释，说明名词的具体内容，一般由that引导，例如：
1) The king’s decision that the prisoner would be t free surprid all the people.
2) The order that all the soldiers should stay still is given by the general.
2. 同位语在句子中的位置
同位语从句有时可以不紧跟在它所说明的名词后面，而是被别的词隔开。例如：
He got the news from Mary that the sports meeting was put off.
3. 同位语从句与定语从句的区别
（1）. 同位语从句和定语从句相似，二者都有先行词。同位语从句是对先行词的进一步陈述，和先行词是同等的关系，含义相同。定语从句是对先行词的修饰或限制。
（2）. 同位语从句表示先行词的内容是什么，进一步说明先行词。定语从句与先行词之间是所属关系，表示“ …的” ，起修饰作用。
（3）. 同位语从句的“ that ” 不能省略。定语从句的关系代词“ that ” 在从句中作宾语时可以省略。
（4）同位语从句的先行词是一个含有概念的抽象名词，从句对这一概念进行展开或说明。
1.正确使用同位语从句的关连词；
2.正确运用同位语从句的先行词；
3.能正确认识并正确翻译同位语从句。
同位语从句和定语从句比较练习
1. I heard about the news that he got a full mark in this examination.（同位语从句）
2. This is good news that I heard from Mary. （定语从句）成功英文
3. He can’t answer the question h ow he got the money. （同位语从句）
4. This is an easy question that he answered in class. （定语从句）
通过以上介绍，我们可以看出，四种名词性从句都需要有一个连接性词在从句的开头。这个词是什么性质，要看它在从句中作作的成分，如果作的是主语、宾语、表语的话，这个词就是连接代词；如果作的是各种状语，就叫连接副词；如果不作任何成分，就叫连接词。
引导名词性从句的连接词：
连接词that, if, whether
连接代词：who, whom, what, who, which, whichever, whatever, whoever
连接副词when, where, how, why
第二节考点分类解析
【考点一：语序问题】
名词性从句的语序：永远陈述语气。即名词性从句中不会出现助动词提前的现象。如：
Who he is doesn’t matter much.
When and where we shall have the sports meet is a question.
I don’t know what his name is.
I don’t know what is wrong with him. = I don’t know what is the matter with him.
You can’t imagine how excited I was at that time.
Can you tell me what size shoes you wear?
No one can be sure ______ in a million years. （MET1991）
A. what will man look like
B. what man will look like
C. man will look like what
D. what look will man like
【考点二：that和what的区别问题】
能引导名词性从句的关系代词有who, whom, what, who, which, whichever, whatever, whoever八个。为何单独讲what的用法呢？重要！在考试中出现的频率高！在本书第一章《定语从句》中，我们提到过，what是不能引导定语从句的。定语从句中如果缺少的成分是主语、宾语、表语，我们选择的是关系代词that或其他。现在山头换了，到了名词性从句的知识范围了。What在名词性从句中就很有用武之地了。还是分析成分，what 在从句中作的主语、宾语、表语。而that只是一个“连接词”，既不作什么成分，也没有什么意义。如:
What you did doesn’t agree with what you promid.
What he couldn’t u nderstand was why his teacher was never satisfied with him.
The matter of salary is what I care most if I decide to change my profession.
What we can’t get always ems better than what we have already got.
I think that your composition is no better than his.
That you don’t love her is not my business.
What we have en is different from _______.
A. we heard
B. we have heard
C. what we heard
D. what we have heard
答案：D。我们应该可以看出这是个宾语从句。从句中hear是个及物动词，缺少宾语。所以，应该选有what引导的从句。而不能是that或者省略了that的情况。
I c ouldn’t agree with ______ at the meeting.
A. that you said
B. which you said
C. all what you said
D. what you said
答案：Ｄ。与上一题相同，这也是一个考查宾语从句的题目。从句中的say是个及物动词，缺少宾语。所以，应该选择what引导的宾语从句。但是，这个题目最容易错的选项是Ｃ。因为有些同学会认为all是先行词，而后面时what 引导的定语从句。但是，what是不引导定语从句的。所以，Ｃ根本就是不存在的。
【考点三：that和whether的区别问题】
有时候，它们两个比较难以区别，因为，它们都是连接词，都在从句中不作成分。但是，它们之间最大的区别在于“意义”。即that在从句中既不作成分，也没有自己的意义；而whether就不同了。它虽然不在从句中作什么成分，但是它又意义，即“是否”。这就能够左右从句的意思，使从句所表达的意思变成一个还没有确定的因素。如：
I don’t know whether he can join us or not.
I’m sure that h e can join us.
It is none of your business whether I love her.
It is none of your business that I don’t love her.
综上所述，区分that还是whether，重要一点就是看主句需要从句表达一个什么意思，是确定的，还是不确定的；是事实还是疑问。前者选that，后者选whether。如：
I have no doubt _____ Mr. Johnson will make it here on time.
A. that
B. whether
C. why
D. when
No one can be sure _____ the board will accept our conditions.
A. that
B. whether
C. why
D. what
【考点四：if和whether的区别问题】
二者在引导宾语从句时都有“是否”之意。但并不是永远可以互换。一般认为，二者可以互换的环境也只有在宾语从句中。如：
He didn’t give us explicit reply whether/if he will attend our wedding ceremony.
而在介词的宾语从句中，在主语从句中，在表语从句中，在同位语从句中，在和不定式搭配的结构中等等，习惯上只能用whether。如：
1. _______ we’ll go camping tomorrow depends on the weather. （1996）
A. If
B. Whether
C. That
D. Where
