名词性从句和定语从句怎么区分

二、语法要点剖析
一、名词性从句
主语从句、表语从句、宾语从句、同位语从句，在整个句子中所起的作用，相当于一个名词。因此，这四种从句通称为名词性从句。
引导名词性从句的连接词可分为三类：
连接词：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
1. 主语从句
作句子主语的从句叫主语从句。主语从句通常由从属连词that，whether，if和连接代词what，who，which，whatever， whoever以及连接副词how，when，where，why等词引导。that在句中无词义，只起连接作用；连接代词和连接副词在句中既保留自己的疑问含义、又起连接作用，在从句中充当从句的成分。例如：
What he wants to tell us is not clear. 他要跟我们说什么，还不清楚。
Who will win the match is still unknown. 谁能赢得这场比赛还不得而知。
It is known to us how he became a writer. 我们都知道他是如何成为一名作家的。
Where the English evening will be held has not yet been announced. 英语晚会将在哪里举行，还没有宣布。
有时为避免句子头重脚轻，常用形式主语it代替主语从句作形式主语放于句首，而把主语从句置于句末。主语从句后的谓语动词一般用单数形式。常用句型如下：
（1） It + be + 名词 + that从句
（2）It + be + 形容词 + that从句
（3）It + be + 动词的过去分词 + that从句
（4）It + 不及物动词 + that 从句
另注意在主语从句中用来表示惊奇、不相信、惋惜、理应如此等语气时，谓语动词要用虚拟语气“(should) +do”，常用的句型有：
It is necessary (important, natural, strange, etc.) that …
It is a pity (a shame, no wonder, etc.) that…
It is suggested (requested, proposed, desired, etc.) that…
2. 宾语从句
名词句用作宾语的从句叫宾语从句。引导宾语从句的关联词与引导主语从句表语从句的关联词大致一样，在句中可以作谓语动词或介词及非谓语动词的宾语。
1. 由连接词that引导的宾语从句
由连接词that引导宾语从句时，that在句中不担任任何成分，在口语或非正式的文体中常被省去，但如从句是并列句时,第二个分句前的that不可省。例如：
He has told me that he will go to Shanghai tomorrow. 他已经告诉我他明天要去上海。
We must never think (that) we are good in everything while others are good in nothing. 我们决不能认为自己什么都好，别人什么都不好。
注意：在demand、order、suggest、decide、insist, desire, demand, request, command等表示要求、命令、建议、决定等意义的动词后，宾语从句常用“（should）+ 动词原形”。例如：
I insist that she (should) do her work alone. 我坚持要她自己工作。
The commander ordered that troops (should) set off at once. 司令员命令部队马上出发。
2. 用who，whom, which, whose, what, when, where, why, how, whoever, whatever, whichever等关联词引导的宾语从句相当于特殊疑问句，应注意句子语序要用陈述语序。例如：
I want to know what he has told you. 我想知道他告诉了你什么。
She always thinks of how she can work well. 她总是在想怎样能把工作做好。
She will give whoever needs help a warm support. 凡需要帮助的人，她都会给予热情的支持。
3. 用whether或if引导的宾语从句，其主语和谓语的顺序也不能颠倒，仍保持陈述句语序。此外，whether与if 在作“是否”的意思讲时在下列情况下一般只能用whether，不用if：
a. 引导主语从句并在句首时；b. 引导表语从句时；c . 引导从句作介词宾语时；d. 从句后有“or not”时；e. 后接动词不定式时。例如：
Whether there is life on the moon is an interesting question. 月球上有没有生命是个有趣的问题。
The question is whether she should have a low opinion of the test?
Everything depends on whether we have enough money. 一切要看我们是否有足够的钱。
I wonder whether he will come or not. 我想知道他来还是不来。
Can you tell me whether to go or to stay? 你能否告诉我是去还是留？
4. 注意宾语从句中的时态呼应，当主句动词是现在时，从句根据自身的句子情况，而使用
不同时态。例如：
he studies English every day. （从句用一般现在时）
he studied English last term. （从句用一般过去时）
I know (that) he will study English next year. （从句用一般将来时）
he has studied English since 1998. （从句用现在完成时）
当主句动词是过去时态（could, would除外），从句则要用相应的过去时态，如一般过去时，过去进行时，过去将来时等；当从句表示的是客观真理，科学原理，自然现象，则从句仍用现在时态。例如：
The teacher told us that Tom had left us for America．
5. think, believe, imagine, suppose等等动词引起的否定性宾语从句中，要把上述主句中的动词变为否定式。即将从句中的否定形式移到主句中。例如：
We don’t think you are here. 我们认为你不在这。
I don’t believe he will do so. 我相信他不会这样做。
3. 表语从句
在句中作表语的从句叫表语从句。引导表语从句的关联词与引导主语从句的关联词大致一样，表语从句位于连系动词后，有时用as if引导。其基本结构为：主语 + 系动词 + that从句。例如：
The fact is that we have lost the game. 事实是我们已经输了这场比赛。
That’s just what I want. 这正是我想要的。
This is where our problem lies. 这就是我们的问题所在。
That is why he didn’t come to the meeting. 那就是他为什么不到会的原因。
It looks as if it is going to rain. 看上去天要下雨了。
需要注意的，当主语是reason时，表语从句要用that引导而不是because。例如：
The reason why he was late was that he missed the train by one minute this morning
4. 同位语从句
同位语从句说明其前面的名词的具体内容。同位语从句通常由that引导，可用于同位语从句的名词有advice、demand、doubt、fact、 hope、idea、information、message、news、order、problem、promise、question、 request、suggestion、truth、wish、word等。例如：
The news that we won the game is exciting. 我们赢得这场比赛的消息令人激动。
I have no idea when he will come back home. 我不知道他什么时候回来。
The thought came to him that Mary had probably fallen ill. 他想到可能玛丽生病了。
同位语从句和定语从句的区别：
that作为关系代词，可以引导定语从句，充当句子成分，在从句中作宾语时可以省略； that引导同位语从句时，起连词的作用，没有实际意义，不充当句子成分，一般不能省略。
试比较下面两个例句:
I had no idea that you were here．（that引导同位语从句，不能省略）
Have you got the idea（that）this book gives you of life in ancient Greece？（that引导定语从句，作宾语，可以省略）

三、高考热点透视
1. ___ is a fact that English is being accepted as an international language. (NMET 1995)
A. There B. This C. That D. It
答案D。当名词从句在句中作主语时，为避免句子头重脚轻，常用it作形式主语置于句首，而将真正的主语从句放在句尾。此时it只起先行引导作用，本身无实义。此句也可以改写为：That English is being accepted as an international language is a fact.
2．A computer can only do ____ you have instructed it to do．（NMET2001）
A．how B．after C．what D．when
答案C。从句子结构可知，句子的空白处应该填引导宾语从句的连词，做主句谓语动词do的宾语，同时该连接词还是从句中的do的宾语，因此，此处的连接词应该用what。
3. He asked ____ for a violin．（MET1992）
A. did I pay how much B. I paid how much
C. how much did I pay D. how much I paid
答案：D。宾语从句相当于特殊疑问句，句子语序要用陈述语序。
4. What the doctors really doubt is my mother will recover from the serious disease soon．（上海2001年春季招生）
A. when B. how C. whether D. why
答案C。这是一个表语从句。根据 doubt一词可知，所怀疑的应是是否能治好病，所以要填whether。这句话的意思是“医生真的怀疑我妈妈是否能很快从重病中恢复过来。”
5．It is generally considered unwise to give a child _____he or she wants. (NMET1997)
A. however B. whatever C. whichever D. whenever
答案B。根据句意“一般认为孩子要什么就给什么是不好的。”可以看出后面的从句应是一个宾语从句，而从句中wants缺少宾语，A. however 和D. whenever是不能作宾语的；排除A和D，whichever表示“无论哪一个，无论哪些”，应表示一定范围内的人或物，此处没有涉及事物的范围，所以应选 B．whatever，表示“无论什么”。
6. ______leaves the room last ought to turn off the lights. (MET1988)
A. Anyone B. The person C. Whoever D. Who
答案C。本题句子的意思是：无论谁最后离开房间一定要把灯关掉。本题考查连接代词whoever引导的名词性从句，连接代词whoever可以引导名词性从句，并在从句中作主语，相当于any person who或The person who, 意为“一切……的人”。而anyone和the person均非连词，不能引导从句，况who leaves the room last意为“某个最后离开房间的人”，与题意不符，如果要选A. Anyone或B. The person，都必须在它们后面再加上引导定语从句的关系代词who。如果要选D. Who就体现不出“无论谁”的含义了。
7. Sarah hopes to become a friend of ______shares her interests. (Shanghai1995)
A. anyone B. whomever C. whoever D. no matter who
答案为C。本题句子的意思是：Sarah希望跟自己有共同爱好的人交朋友。疑问词+ever引导的名词性从句与no matter+疑问词引导的从句的区别是：前者既可以引导名词性从句也可以引导让步状语从句；后者只能引导让步状语从句。首先排除A和D，从句中需要的是主语，所以whomever也不行。
8. ---- I drove to Zhuhai for the air show last week.
---- Is that ______ you had a few days off ? ( NMET1999)
A. why B. what C. when D. where
答案A。根据语境，甲说上周驱车去珠海观看航模展览。乙据此来询问甲这是否是请几天假的原因，故答案是A。答案B,C, D均与该题语境不符。根据上句提供的语境，下句应该问“那就是你为什么离开几天的原因吗？”
9. I still remember ______ this used to be a quiet village. ( NMET1993)
A. when B. how C. where D. what
答案A。根据从句中缺少的句子成分是状语，排除D．what，而答案C, D均与题意不符，所以应选A．when。used to be表示一种过去存在的状态，本句的意思是“我仍然记得这里在什么时候是个宁静的地方。”
10．I read about it in some book or other，does it matter ____ it was？（2001春季招生）
A．where B．what C．how D．which
答案D。这是一个主语从句。主语从句中缺少表语。从上句的意思分析，应是哪本书，所以要填which，这句话的意思是“我在某本书中读到过有关这方面的内容，是哪一本书重要吗？”。
11. Information has been put forward ____ more middle school graduates will be admitted into universities.
A. while B. that C when D. as (2001年上海)
答案B。该题考查that引导的同位语从句。同位语从句通常由that引导，接在fact, news, promise, possibility, information, doubt, message名词后，用来解释或说明名词的内容。
12. —I think it is going to be a big problem.
—Yes, it could be.
—I wonder ______ we can do about it. (北京 2002春季)
A、if B、how C、what D、that
答案C。本题考察名词性从句的连接词的用法。wonder后面应跟宾语从句，而从句中的谓语动词do是及物动词，可见从句缺少一个代替宾语的成分，我们可以用排除法排除不作成分的if和that，再排除引导方式状语的how，答案是C，句子的意思是“我们能就此做些什么”。
四、专项考点练习
1. ________that they found an unusual plant in the forest.
A. It is said B. They are said C. It said D. It says
2. _____ caused the accident is still a complete mystery.
A. What B. That C. How D. Where
3. It worried Mary a lot _____ she would pass the college entrance examination.
A. whether B. if C. that D. how
4. Shanghai has taken on a new look. It isn’t like _____ it used to be .
A .what B. how C. that D. which
5. ____ is no possibility ______ Bob will win the first prize in the match.
A. There, that B. It, that C. There, whether D. It, whether
6. Little Tommy was reluctant to tell the schoolmaster ____ he had done the day before.
A .that B. how C .what D. where
7. The old man smiled when he saw how pretty _____ up to be during the past few years.
A. had his daughter grown B. would his daughter grow
C. his daughter would grow D. his daughter had grown
8. Have you seen Mary lately? My boss wants to know _______.
A. how she is getting along B. how is she getting along
C. what she is getting along D. what is she getting along
9. ____surprised me most was _____such a little girl of seven could play the violin so well.
A. That; what B. What; that C. That; that D. What; what
10. These wild flowers are so special I would do ______ I can to save them.
A. whatever B. which C. that D. whichever
11. _____ helped to save the drowning girl is worth praising.
A. Who B. Anyone C. Whoever D. The person
12. Eat _____ you like and leave the others for _____ comes in late.
A. any; who B. every; whoever C. whichever; whoever D. either; whoever
13. ____ she couldn’t understand was _____ fewer and fewer students showed interest in her lessons.
A. What; why B. That; why C. What; because D. Why; that
14. It was ____ he said ___ disappointed me.
A. What; that B. That; that C. What; what D. That;what
15. It was ordered that all the soldiers _______to the front.
A. should send B. must be sent C. should be sent D. must go
16. The true value of life is not in ______, but _______.
A. which we get; what give we B. what we get; what we give
C. which do we get; what do we give D. how we get; that we give
17. We are all for your proposal that the discussion _______.
A. be put off B. was put off C. should put off D. is to be put off
18. Go and get your coat．It's ____ you left it．
A. where B. there C. here where D. where there
19. Sarah hopes to become a friend of ______ shares her interests.
A. anyone B. whomever C. whoever D. no matter who
20. You can’t imagine ______ when they received these nice Christmas presents.
A. how they were excited B. how excited they were
C. how excited were they D. they were how excited
Keys: 1---5 A A ABA 6---10 CDABA 11----15 CCAA C 16---20 BAACB

参考资料：http://baike.baidu.com/view/414544.htm
回答者： rainhat1 - 初入江湖 三级 9-9 07:14
http://baike.baidu.com/view/414544.htm
名词性从句
在句子中起名词作用的句子叫名词从句 (Noun Clauses）。 名词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。

一、高考焦点指南在复合句中起名词作用的从句叫做名词性从句。它包括主语从句、宾语从句、表语从句和同位语从句。名词性从句是中学阶段的一个重要语法项目，在历年的高考中几乎都涉及到，并且每年的命题各有变化。分析历届高考试题名词性从句考查的焦点主要有以下六个方面
1. 考查名词性从句的语序问题
高考真题例示：
例1. The photographs will show you ____．（MET1989）
A. what does our village look like B. what our village looks like
C. how does our village look like D. how our village looks like
例2. Someone is ringing the doorbell. Go and see ___________. (NMET2000)
A. who is he B. who he is C. who is it D. who it is
例3. Can you make sure ______ the gold ring? (NMET1990)
A. where Alice had put B. where did Alice put
C. where Alice has put D. where has Alice put
例4. He asked ________ for the violin. (NMET1991)
A. did I pay how much B. I paid how much
C. how much did I pay D. how much I paid
2. 考查引导词that与what的区别
高考真题例示：
例1. ______we can’t get seems better than ______we have. (NMET1996)
A. What; what B. What; that C. That; that D. That; what
例2. No one can be sure _____ in a million years. (MET1991)
A. what man will look like B. what will man look like
C. man will look like what D. what look will man like
例3. _______ you have done might do harm to other people. (MET 1987)
A. That B. What C. Whether D. How
例4. _______ you don't like him is none of my business. (上海1992)
A. What B. Who C. That D. Whether
3. 考查it在名词性从句中作形式主语或形式宾语的用法
高考真题例示：
例1. _____ is a fact that English is being accepted as an international language. (NMET1995)
A. There B. This C. That D. It
例2. It worried her a bit ______her hair was turning grey.
A. while B. if C. that D. for
例3. I hate _____when people talk with their mouths full. (NMET1998)
A. it B. that C. this D. them
例4. Does _______ matter if he can't finish the job on time? (MET 1991)
A. this B. that C. he D. it
4. 考查whether与if的区别
高考真题例示：
例1. _____we’ll go camping tomorrow depends on the weather. (NMET1996)
A. If B. Whether C. That D. Where
例2. What the doctors really doubt is _____my mother will recover from the serious disease soon. (上海2001)
A. when B. how C. whether D. why
例3. _____ the 2000 Olympic Games will be held in Beijing is not known yet. (MET1992)
A. Whenever B. If C. Whether D. That

是差主语吧
因为它是只代city
city是先行词，是对它的补充
就是这个城市，一个怎样的城市是……

懵了……

从句是在整个句子中作状语的成分
而what在从句中作主语的句子
where是副词 副词前不能加介词