同位语从句和主语从句的区别

一.引导定语从句的关联词包括关系代词和关系副词。关系代词有that, which, whose, who, whom, as；关系副词有when, where, why。关系代词和关系副词在定语从句中都充当一定的句法成份。关系代词在从句中充当动词的宾语时一般可以省略。
关系代词的选用比较复杂，受下列条件的制约：
(1) 要看先行词是指人还是指物，
(2) 要看关系代词在从句中句法功能，
(3) 要看定语从句是限定性的还是非限定性的。

在定语从句中充当的成分
↓ 用于限定性或非限定性从句 只用于限定性从句
指人 指物 指人或指物
主语 who which that
宾语 whom which that
谓语 whose whose (of which)
That 只能用在限定性定语从句中，而who, whom, which, which 既可用于限定性定语从句中，也可用于非限定性定语从句。
I know that he is a man who means what he says.
I know that he is a man that means what he says. 【我知道他是一个守信用的人。】

The gentleman whom she met addressed her with courtesy.
The gentleman that she met addressed her with courtesy. 【她遇到的那位先生很有礼貌地向她打了招呼。】
The gentleman she met addressed her with courtesy.（在从句中充当动词宾语的关系代词，可以省略。）

The watch which was lost has been found.
The watch that was lost has been found. 【丢了的表找到了。】

Here is the material which you need. (注：现代美语中不允许这样用)
Here is the material that you need.
Here is the material you need. 【你要的材料在这儿了。】

You are the only one whose advice he might listen to. 他也就是听你的话吧。

关系副词的选用相对来说比较简单，如果先行词是表示时间的名词，如time, day 等，则用when, 如先行词为表示地点的名词，如place, house, area 等等，则选用where。如果先行词为reason 则选用why

I will never forget the mountain village where I spent my childhood.
I will never forget the mountain village in which I spent my childhood.
我永远也不会忘记我度过童年的那个小山村。

I don’t know the reason why he did that.
I don’t know the reason for which he did that. 【我不知道他为什么这么做。】

当先行词是all, something, nothing 等不定代词时，或者先行词的前面有first, last, only, few, much, some, any, no 等词修饰时，或者先行词的前面有最高级修饰时，一般只用that 而不用which 来引导定语从句：
I have explained everything that I can to you.
I have explained everything I can to you. 【我已经尽一切可能把事情向你解释得一清二楚。】

This is the most beautiful campus that I have ever been to.
This is the most beautiful campus I have ever been to. 【这是我见到的最美丽的校园。】

That’s all that I know.
That’s all I know. 【我知道的就是这些。】

Can you tell me something that you know?
Can you tell something you know? 【你能把你知道的一些情况告诉我吗？】

There is nothing that I cannot tell you.
There is nothing I cannot tell you. 【我没有什么不能告诉你的事情。】

The first thing that we should do is to work out a plan.
The first thing we should do is to work out a plan. 【我们应该做的头一件事就是订一个计划。】

The last place that we visited was the farm.
The last place we visited was the farm. 【我们最后参观的地方是农场。】

还有一种定语从句，它的结构是：the same ….. as…, such … as
这里的as 可以指人或物，这里的as 引导的是限定性定语从句：
Such furniture as is very popular is expensive. 一种很受欢迎的家具价钱昂贵。
We have successfully done the same experiment as you did. 你做过的那个试验我们已经成功地做完了。
It wasn’t such a computer as the advertisement had promised. 这种电脑可不是广告中说的那种电脑。

限定性定语从句与主句关系密切，为句中不可缺少的部分，如去掉，主句意思就不完整了。而非限定性定语从句与主句关系松散，如果去掉了，主句内容仍然完整。在书面语中非限定性定语从句一般补逗号隔开。非限定性定语从句一般不用that 引导。引导非限定性定语从句的关系词不可省略。
His speech, which bored everyone, went on and on. 他的讲话没完没了，真让人烦。
The general’s daughter, whose name is Jane, gave me a sweet smile.
将军的女儿名叫珍妮。她冲我笑了笑，笑得好甜啊。

非限定性定语从句中，先行词也可以是整个句子，一般用which 或as 来引导定语从句，which在从句中可充当主语、宾语等，as 在从句中一般只充当主语，which 与as 引导这类定语从句的区别在于：which 只能放在句子当中或句子末尾，而as 的位置比较灵活，可以放在句子当中、句子末尾，也可以放在句首。
As is known to all, too much stress can cause disease.
Too much stress can cause disease, as is known to all.
Too much stress can cause disease, which is known to all. 【众所周知，压力太大了，人会得病的。】

Water consists of hydrogen and oxygen, which is known to all.
Water consists of hydrogen and oxygen, as is known to all. 【众所周知，水是由氢和氧组成的。】

关系代词在定语从句中有时也作介词的宾语。如果介词被置于关系代词前，一般只用介词加which 或介词加whom，而不用介词加that来引导定语从句。如果介词被置于从句句末，则可以使用that来代替which或whom，这时的that可以省略。
This is the ring on which she spent 1,000 dollars. 这就是她花了一千美元买的那枚戒指。

One of my colleagues whom you are familiar with will come today.
One of my colleagues that you are familiar with will come today.
One of my colleagues you are familiar with will come today.
我的一个同事，就是你非常熟悉的那个人，今天要过来。
二.同位语从句是指在复合句中跟在名词后面，充当名词的同位语的从句，它是对前面的名词起到解释和说明的作用。同位语从句常位于news,idea,fact,thought,problem,answer,belief,possibility，plan,suggestion,promise,teport,question,truth,proof,order,hope,information...等的名词后面。例如：
1、The news that the famous singer will come to our city is not true.
那位著名的歌星将要到我们市的消息是不真实的。
（其中that引导的同位语从句只是对名词The news的内容进行解释。）

2、She made a promise that she would give me a present on my birthday.
她许下诺言在我生日的时候将送我一份礼物。
（其中that引导的同位语从句只是对名词a promise的内容进行解释。）

3、I have no idea when he will come back.
我不知道他什么时候回来。
（其中when引导的同位语从句只是对名词idea的内容进行解释。）

4、The question who should come with me has not been settled.
谁将和我一起去这个问题还没解决。
（其中who引导的同位语从句只是对名词The question的内容进行解释。）

同位语从句的引导词有：
that,whether,who,when,where
其中that只起到引导从句的作用，它在从句中不充当任何成分，没有意义，但也不能省略。

主语从句的功能是一个句子当做主语来用
比如: (我爱的人)不爱我.
(Whom I love) doesn't love me.
主语从句通常位于句首，或在It作形式主语的句子中放在句尾。

.同位语从句是指在复合句中跟在名词后面，充当名词的同位语的从句，它是对前面的名词起到解释和说明的作用。同位语从句常位于news,idea,fact,thought,problem,answer,belief,possibility，plan,suggestion,promise,teport,question,truth,proof,order,hope,information...等的名词后面。例如：
The news that the famous singer will come to our city is not true.
那位著名的歌星将要到我们市的消息是不真实的。
（其中that引导的同位语从句只是对名词The news的内容进行解释。）

She made a promise that she would give me a present on my birthday.
她许下诺言在我生日的时候将送我一份礼物。
（其中that引导的同位语从句只是对名词a promise的内容进行解释。）

同位语从句的引导词有：
that,whether,who,when,where
注意！★：其中that只起到引导从句的作用，它在从句中不充当任何成分，没有意义，但也不能省略。

最主要的就是定语从句是句子做定语了，而主语从句是从句做主语滴

同位语从句能接在先行词之后