►同位语从句
同位语从句是对名词的内容给予具体、详细的说明。常在后面接同位语从句的名词有fact, news, idea, truth, hope, suggestion, question, problem, doubt, fear, belief等。同位语从句常用的引导词为that,有是也用when, where 等疑问词。如：
The news that the United States was hit by terrorist attacks took the whole world by surprise. 美国受到恐怖主义分子袭击的消息令全世界吃惊。
The idea that you can do this work well without thinking is quite wrong. 你认为不动脑筋就能做好这件工作的想法是完全错误的。
People used to hold the belief that the earth was the center of the universe. 人们曾认为地球是宇宙的中心。
The difficulty lies in the fact that we are short of money. 困难在于我们缺乏资金这个事实。
They have no idea at all where he has gone. 他们一点儿也不知道他去哪儿了。
注意：同位语从句的that 只是引导词，没有其他语法作用，在句子中不作句子成分，不能省略;而定语从句中的that 除了引导定语从句外，还是定语从句的一个成分，在定语从句中作主语或宾语，作主语时不能省略，作宾语时可以省略。如：
The idea that some peoples are superior to others is sheer nonsense. 有些民族优越于其他民族这种想法简直荒谬。(同位语从句)
The idea that he proposed at the meeting is sheer nonsense. 他在会议上提出的这个想法简直荒谬。(定语从句)
No one is happy with the fact that he found out. 没有人对他发现的事实感到高兴。(定语从句)
No one is happy with the fact that he will become their boss. 没有人对他将成为他们的老板这一事实感到高兴。(同位语从句)
►关系代词
指人的关系代词：who, whom, whose, that 的用法：
(1) 作主语(who, that )
Those who are going to play in the match are to meet at the gate at 1:30 after lunch.
那些参加比赛的人午饭后1：30在大门口集合。
在本句中，先行词是those;关系代词who引导定语从句，同时代替先行词在从句中担任动词are going to play 的主语。
The man who/that is talking with Mr. Wang is a famous doctor.
正在和王先生说话的那个人是一个有名的医生。
在本句中，先行词是the man;关系代词who/that引导定语从句，同时代替先行词在从句中担任动词is talking的主语。
这个复合句可以还原成两个句子：The man is a famous doctor. He is talking with Mr. Wang.
(2) 作宾语包括作介词宾语(whom, that )。此种情况下的关系代词可以省略;
This is just the man (whom/that) I want for the job.这正是我要的做这份工作的人。
在本句中，先行词是the man；关系代词whom/that引导定语从句，同时代替先行词在从句中担任动词want 的宾语。
Is he the manager (whom/that) you are looking for?
他是你在找的那位经理吗?
(3) 当关系代词紧跟介词作介词宾语时，不能用that，也不能省略，
如：The book from which I got a lot of useful information was written by a famous scientist.
我从中得到许多有用信息的那本书是一位科学家写的。
Who is the boy with whom you were talking a moment ago.
你刚才和他说话的那个男孩是谁?
I know the young couple from whose house the music is coming.
但是当介词放在从句末尾时，作为介词宾语的关系代词可以用that 并且可以省略。
如上头两句可改为：
The book (that /which) I got a lot of information from was written by a famous scientist.
Who is the boy (that/whom) you were talking with a moment ago?
