名词性从句与定语从句的区别

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。

定语从句
定语从句是由关系代词和关系副词引导的从句，其作用是作定语修饰主句的某个成分，定语从句分为限定性和非限定性从句两种。

状语从句分为时间状语从句，结果状语从句，让步状语从句，原因状语从句，条件状语从句以及行为方式状语从句。

名词从句包括主语从句，宾语从句，表语从句和同位语从句及there be 句型
名词性从句包括主语从句、宾语从句、表语从句和同位语从句。

引导名词性从句的连接词按其在从句中所起的作用分为：
1）连接代词：who(-ever), what(-ever), which(-ever), whom(-ever), whose
2）连接副词：when, where, why, how
3）连接词：that, whether, if
连接代词和连接副词在从句中充当一定的句子成分，而连接词在从句中不充当句子成分，只起连接作用。

1．主语从句
在主句中充当主语的从句叫主语从句，它位于主句的谓语动词之前。

但实际使用中常用it作形式主语，而把主语从句移到主句之后。

例如：
Who will go makes no difference.
It makes no difference who will go.
That she was able to come made us very happy.
It made us happy that she was able to come.
注意：由what, whoever, whatever, whichever引导的主语从句一般不后置。

2．表语从句
位于主句中系动词之后，在主句中充当表语的从句叫表语从句。

例如：
One advantage of living in the country is that one can get close to nature.
His mother was ill and he had to look after her. That was why he was late.
表语从句常见于be动词之后，有时见于look之后；引导表语从句的连接词除前面所列的常用词之外，还可由because, as if/though引出。

例如：
He was late. That was because he had to look after his sick mother.
(=The reason was that he had to look after his sick mother.)
It looks as if/though it is going to rain.
They looked as if/though they had been friends for many years.
3．宾语从句
在主句中位于及物动词之后或少数介词之后、充当主句宾语的从句叫宾语从句。

宾语从句中的that通常可以省略。

例如：
I doubt whether/if he will be against the idea.
She will write a book on how young mother should raise their babies.
I know nothing about him except that he lives next door.
当及物动词后跟两个(或两个以上)的宾语从句时，只有第一个that可以省去，后面从句中的that通常不省去。

如：
He said (that) the text was very important and that we should learn it by heart.
跟在一些表示情感意义的形容词（如afraid, glad, happy, pleased, sorry, anxious, worried, surprised, disappointed等）或确信意义的形容词（如certain, sure 等）后的从句通常也被当作宾语从句对待，其中that 也可以省略。

例如：
I’m not sure whether/if I can pass the exam successfully.
如果主句的谓语是make, find, feel, believe, think, suppose, consider, see to等常带有宾语补足语的动词，则通常在这些词后用it作形式宾语，而把宾语从句置于宾语补足语之后，其结构通常是“动词+it+宾补+宾语从句”。

例如：
He thought it a pity that he missed the film.
We find it necessary that we (should) practise spoken English every day.
4．同位语从句
跟在名词后面、进一步说明该名词的具体内容的从句叫同位语从句。

可以带同位语从句的名词主要是一些可加进具体内容的、表示信息、思想等概念的抽象名词，如news, fact, idea, hope, belief, truth, promise, thought, fear, doubt, possibility, order, suggestion, proposal等。

同位语从句与其前面的名词是同等关系，引导同位语从句最常用的是that，that在从句中不充当任何成分，只起连接作用，一般不能省略。

例如：
We are surprised at the fact that the children did it all on their own.
I made a promise that if anyone set me free, I would make him very rich.
They expressed the hope that we would go and visit Germany again.
that引导的同位语从句与定语从句的区别：
The suggestion that the students (should) have plenty of exercise is very good.
The suggestion (that/which) he raised at the meeting is very good.
对比发现上句中的that只起连接作用，在从句中不充当任何成分，因此它引导的是同位语从句，其中that 不能省略；下句中that不仅起引导作用，同时在从句中还充当了动词raised的宾语，因此它是定语从句，此时that可用which代替，又因其在定语从句中充当宾语，故又可省略。

名词性从句的难点把握
1．由whoever/whatever/whichever/whomever引导的名词性从句
这些词引导的名词性从句相当于带有定语从句的名词词组：
whoever=anyone who…“任何……的人”；whomever是whoever的宾格形式
whatever=anything that… “任何……的物”
whichever=any … that… “任何……的（已知范围内的或上文提到过的）人或物”
它们可以用来引导主语从句，例如：
Whoever leaves the room last ought to turn off the light.
=Anyone who leaves the room last ought to turn off the light.
Whatever he had was seized by the German soldiers.
=Anything that he had was seized by the German soldiers.
Whichever of you comes in first will receive a prize.
=Any one of you who comes in first will receive a prize.
这些词还可以用来引导宾语从句，例如：
You can just say whatever comes to your mind.
=You can just say anything that comes to your mind.
Take whichever seat you like.
=Take any seat that you like.
You may choose whoever/whomever you’d like to go with.
=You may choose anyone who you’d like to go with.
( 注：whoever在主句中作choose的宾语，在从句中又充当go with的宾语，因此可用宾格的whomever来
代替)
She would like to make friends with whoever shares her interest.
=She would like to make friends with anyone who shares her interest.
（注：whoever在主句中作介词with的宾语，但在从句中又充当谓语动词shares的主语，因此不能用whomever代替）
关于—ever等词引导让步状语从句的用法可参阅本章第三节“状语从句”。

2．名词性从句中的what和that
what和that的选用一直是学生学习的一个难点，正确选择的关键是看该从句结构是否相对
完整、是否缺少主语、宾语或表语等成分而定。

例如：
What he said at the meeting surprised everybody present.
That he said nothing at the meeting surprised everybody present.
The problem is what we should do to protect the earth.
The fact is that we should do something to protect the earth.
比较上面两组句子，不难发现，what在句中不仅引导从句，同时它本身在从句还充当了宾
语的作用；没有了what，从句结构就不完整；而that只起引导从句的作用，本身在从句中不充当任何成分，that引导的是一个结构相对完整的陈述句。

3．名词性从句中的whether和if
在主语从句、表语从句和同位语从句中遇“是否”句用whether引导而不用if；在宾语从句中whether和if常可换用。

例如：
Whether the 2000 Olympic Games will be held in Beijing is not known yet. (主语从句，不用if)
The problem is whether we finish the task on time. (表语从句，不用if)
The problem whether we’ll build another school hasn’t been settled. (同位语从句，不用if)
I wonder whether/if the news is true.（宾语从句，可以换用）
但若有or not紧跟其后，不宜用if；介词后面的宾语从句也不用if引导。

例如：
I wonder whether/if the news is true or not.（or not 放在句末，可用if）
I wonder whether or not the news is true. （or not 紧跟其后，不用if）
It depends on whether you want to do it or not. （介词后面的宾语从句，不用if）
4．名词性从句中的虚拟语气
表示“坚持、命令、建议或要求”等词义出现时，不管是在哪一种从句中，常用虚拟语气，从句中的谓语动词形式为（should）+ 动词原形，其中should可省略。

常用词有insist, suggest, order, demand等。

例如：He suggested that a meeting (should) be held immediately. （宾语从句）
It was suggested that a meeting (should) be held immediately. （主语从句）
His suggestion was that a meeting (should) be held immediately. （表语从句）
He made a suggestion that a meeting (should) be held immediately. （同位语从句）
The doctor ordered that she (should) stay in bed for a few days. （宾语从句）
It was ordered by the doctor that she (should) stay in bed for a few days. （主语从句）
The docto r’s order was that she (should) stay in bed for a few days. （表语从句）
The doctor’s order that she (should) stay in bed for a few days was reasonable. （同位语从句）
用来说明主句中某一名词或代词（有时也可说明整个主句或主句中一部分）而起定语作用的句子叫作定语从句。

一．词引导的定语从句
1. 关系代词用来指代先行词是人或物的名词或代词
句子成分用于限制从句或非限制性从句只用于限制性从句
代替人代替物代替人或物
主语Who which that
主语Whom which that
宾语Whose(=of whom)whose(=of which)
例１：This is the detective who came from London.
例２：The book which I am reading is written by Tomas Hardy.
例３：The desk whose leg is broken is very old.
例４：This is the room that Shakespeare was born in.
２．关系代词的用法
(1) 如果先行词是all, much, anything, something, nothing, everything, little, none等不定代词，关系代词一般只用that，不用which。

例如：
All the people that are present burst into tears.
(2) 如果先等词被形容词最高级以及first, last, any, only, few, mush, no, some, very等词修饰，关系代词常用that,不用which, who，或whom。

例如：
(3) 非限制性定语从句中，不能用关系代词that,作宾语用的关系代词也不能省略。

例如：
There are about seven million people taking part in the election, most of whom、are well educated.
(4) which还有一种特殊用法，它可以引导从句修饰前面的整个主句，代替主句所表示的整体概念或部分概念。

在这种从句中，which可以作主语，也可以作宾语或表语，多数情况下意思是与and this 相似，并可以指人。

例如：
He succeeded in the competition, which made his parents very happy.
(5) that可指人或物，在从句中作表语，（指人作主语时多用who）仅用于限制性定语从句中。

(6) which可作表语，既可指人，以可指物。

指人时，一般指从事某种职业或是有种特征．品性或才能的人。

Which引导的定语从句可以限制性的，也可以是非限制性的。

(7) 如果作先作词的集体名词着眼于集体的整体，关系代词用which;若是指集体中的各个成员，则用who。

(8) 先行词有两个，一个指人，一个指物，关系代词应该用that。

例如：
The boy and the dog that are in the picture are very lovely.
(9) 如果先行词是anyone, anybody, everyone, everybody, someone, somebody,关系代词应该用who 或whom，不用which。

例如：
Is there anyone here who will go with you?
３．“介词＋关系代词“是一个普遍使用的结构
(1) “介词＋关系代词“可以引导限制性定语从句，也可以引导非限制性定语从句。

“介词＋关系代词“结构中的介词可以是in, on, about, from, for, with, to at, of, without 等，关系代词只可用whom或which,不可用that 。

(2) from where为“介词＋关系副词“结构，但也可以引导定语从句。

例如：
We stood at the top of the hill, from where we can see the town..
(3) 像listen to, look at, depend on, pay attention to, take care of等固定短语动词，在定语从句中一般不宜将介词与动词分开。

例如：
This is the boy whom she has taken care of.
二．关系副词引导的定语从句
1．关系副词也可以引导定语从句
关系副词在从句中分别表示时间．地点或原因。

关系副词when在从句中充当时间状语，where 充当地点状语，why充当原因状语。

2. that可引导定语从句表示时间．地点或原因
That有时可以代替关系副词when, where 或者why引导定语从句表示时间．地点或原因，在that引导的这种定语从句中，that也可以省去。

三．限制性定语从句与非限制性定语从句
1．二者差异比较
限制定语从句紧跟先行词，同先行词这间一般不加逗号，仅修饰先行词，可以由关系代词．关系副词或that来引导。

非限制性定语从句仅作补充或说明，用逗号与主句隔开，既可修饰先行词，又可修饰整个主句，不可用that引导。

2．关系代词和关系副词的选择依据
(1) 弄清代替先行词的关系词在从句中作什么成分,作状语的应选用关系副词，作主语．宾语或表语的可选用关系代词。

3.先行词与定语从句隔离
定语从句一般紧跟在先行词之后，但定语从句与先行词之间有时也会插入别的成分，构成先行词与定语从句的隔离。

例如：
1) This is the article written by him that Is poke to you about..
2) He was the only person in this country who was invited
四．As在定语从句中的用法
1. 引导限制性定语从句和非限制性定语从句
（１）as多与such 或the same连用，可以代替先行词是人或物的名词。

（２）as 也可单独使用，引导非限制性定语从句，作用相当于which。

例如：
The elephant’s nose is like a snake, as anybody can see.
（３）the same… that与the same …as在意思上是不同的。

2．As引导的非限制性定语从句的位置
as引导的非限制性定语从句位置较灵活，可以位于主句前面．中间或后面，一般用逗号与主句隔开，但which所引导的非限制性定语从句只能放在主句之后。

例如：
(1) As is expected, the England team won the football match.
(2) The earth runs around the sun, as is known by everyone.。