同位语部分是个句子,就是同位语从句,这种用法比较"固定",把关键的几个词背下来.
下面这个材料供参考.
基本概念
1． 定义：用作表语的从句叫做表语从句.
2． 构成：关联词+简单句
3． 引导表语从句的关联词的种类：
(1) 从属连词that.如：
The trouble is that I have lost his address. 麻烦是我把他的地址丢了.
(2) 从属连词whether, as, as if.如：
He looked just as he had looked ten years before. 他看起来还与十年前一样.
The question is whether they will be able to help us. 问题是他们是否能帮我们.
注：从属连词if一般不用来引导表语从句,但as if却可引导表语从句,如：
All this was over twenty years ago, but it´s as if it was only yesterday.
这都是20多年前的事了,但宛如昨天一样.
能跟表语从句的谓语动词一般为系动词be, seem, look等.如：
It looked as if it was going to rain. 看起来天要下雨了.
(3)连接代词who, whom, whose, what, which, whoever, whatever, whichever
连接副词 where, when, how, why.
如：The problem is who we can get to replace her. 问题是我们能找到谁去替换她呢.
The question is how he did it. 问题是他是如何做此事的.
That was what she did this morning on reaching the attic. 那就是她今晨上了阁楼干的.
重点疑难
1． 连词because可引导表语从句.如：
I think it is because you are doing too much. 我想这是因为你做得太多.
2． 在一些表示“建议、劝说、命令”的名词后面的表语从句中,谓语动词用虚拟语气.should+动词原形表示,should可省略.如：
My suggestion is that we (should) start early tomorrow. 我的建议是我们明天一早就出发.
在复合句中,修饰某一名词或代词的从句,称为定语从句,也叫形容词性从句.定语从句和同位语从句容易混淆.
?在英语复合句中,有些定语从句和同位语从句从表面形式上看非常相似,使许多人难以分辨彼此.本文拟从先行词和引导词两个方面对二者进行区别.
?一、先行词
?1．定语从句的先行词是名词或代词；而同位语从句的先行词只能是名词,而且仅限于idea,plan, fact,theory,promise,hope,news,doubt,truth,information,suggestion,question, thought,belief,conclusion等少数名词.例如：
?①The boy who is playing football is my classmate．
?②Those who work hard will succeed．
?③The fact that he had not said anything surprised everybody．
?④The fact that you are talking about is im portant．
?在①句中,划线部分是定语从句,其先行词是名词 boy,它不能用作同位语从句的先行词.
?在②句中,划线部分也是定语从句,其先行词是代词those,代词不能用作同位语从句的先行词.
?在③句中,划线部分是同位语从句,其先行词是名词fact,它同样可以用作定语从句的先行词,④句便是一例.
?由以上分析可见,同位语从句的先行词一定可以用作定语从句的先行词,但定语从句的先行词不一定能用作同位语从句的先行词.
?2．when,where,why引导的定语从句的先行词一定分别是表示时间、地点和原因的名词,而三者引导的同位语从句的先行词则肯定不是表示时间、地点和原因的名词.例如：
?①I still remember the day when I first came to Beijing．
?②I have no idea when she will be back．
?在①句中,划线部分是when引导的定语从句,其先行词day是表示时间的名词；在②句中,划线部分是when引导的同位语从句,其先行词idea则不是表示时间的名词.
?二、引导词
?定语从句和同位语从句共同的引导词有四个：that,when,where,why.下面把四个引导词
?分成两类说明它们在两种从句中的不同用法.
?1．引导词that
?引导定语从句的that叫做关系代词,它除了起连接作用,还在定语从句中充当一定成分,并且在意义上代表先行词；引导同位语从句的that叫做从属连词,它只起连接作用.例如：
?①The news that you told me yesterday was really exciting．
?②We heard the news that our team had won．
?在①句中,划线部分是定语从句,that在从句中作宾语,在意义上指代先行词news.在②句中,划线部分是同位语从句,that没有任何意义,只起连接作用.
?2．引导词when,where,why
?引导定语从句时,它们叫做关系副词,在从句中充当状语,可以转换成"介词＋关系代词"的形式；引导同位语从句时,它们叫做连接副词,在从句中充当状语,但不能转换成"介词＋关系代词"的形式.例如：
?①I will never forget the day when I joined the army．
?②We have no idea when she was born．
?在①句中,划线部分是定语从句,when在从句中作状语,它可以转换成on which的形式；在②句 中,划线部分是同位语从句, when在从句中充当状语,但不能转换成"介词＋关系代词"的形式.
?③This is the house where I lived two years ago．
?④He put forward to the question where the meeting would be held．
?在③句中,划线部分是定语从句,where在从句中作状语,它可以转换成in which的形式；在④句?中,划线部分是同位语从句, where在从句中充当状语,但不能转换成"介词＋关系代词"的形式.
?⑤This is the reason why she will not attend the meeting．
?⑥The teacher had no idea why Jack was absent．
?在⑤句中,划线部分是定语从句,why在从句中作状语,它可以转换成for which的形式；在⑥句 中,划线部分是同位语从句,why在从句中充当状语,但不能转换成"介词＋关系代词"的形式.