在主从复合句中作同位语的从句称为同位语从句。同位语从句一般用that, whether，what, which, who, when, where, why, how 等词引导，常放在fact, news, idea, truth, hope, problem, information, wish,promise, answer, evidence, report, explanation, suggestion, conclusion等抽象名词后面，说明该名词的具体内容。换言之，同位语从句和所修饰的名词在内容上为同一关系，对其内容作进一步说明。
例：The news that they had won the game soon spread over the whole school.他们比赛获胜的消息很快传遍了整个学校。
析：they had won the game说明The news的全部内容，因此该句为同位语从句。
例：The general gave the order that the soldiers should cross the river at once.将军下达了战士们立即过河的命令。
析：the soldiers should cross the river at once是the order的全部内容，且意义完整，因此应用that引导同位语从句。
例：We'll discuss the problem whether the sports meeting will be held on time.我们将讨论运动会是否会如期举行的问题。
析：the sports meeting will be held on time意义不完整，应加"是否"的含义才能表达the problem的全部内容，因此应用whether引导同位语从句。
3.如同位语从句意义不完整，需增加"什么时候"、"什么地点"、"什么方式"等含义，应用when, where, how等词引导同位语从句。
例1：I have no idea when he will be back.
析：he will be back意义不完整，应加"什么时候"的含义才能表达idea的全部内容，因此应用when引导同位语从句。
例2：I have no impression how he went home, perhaps by bike. 析：he went home意义不完整，应加"如何"的含义才能表达impression的全部内容，因此应用how引导同位语从句。
如：The thought came to him that maybe the enemy had fled the city.
如：The report that he was going to resign was false.
因为the report was that he was going to resign 句意通顺，所以，that he was going to resign 是同位语从句。
1）Information has been put forward ____ more middle school graduates will be admitted into universities.
A. while B. that C. when D. as
析：答案为B。more middle school graduates will be admitted into universities是Information的内容，且Information不在从句中作成分，所以该句为同位语从句。应将该句区别于：
2）It is said that more middle school graduates will be admitted into universities，this is the information ____ has been put forward.
A. what B. that C. when D. as
析：答案为B。that has been put forward为information的修饰性定语，且information在从句中作主语，所以该句为定语从句。
例2：She heard a terrible noise,____ brought her heart into her mouth.(MET91)
A. it B. which C. this D. that
析：答案为B。分析语境含义、句子结构和句子成分可知，该句为非限制性定语从句，先行词为a terrible noise，且它在从句中作主语。应将该句区别于：
I can't stand the terrible noise ____ she is crying loudly.
A. it B. which C. this D. that
析：答案为D。she is crying loudly是the terrible noise的.内容，且the terrible noise不在从句中作成分，所以该句为同位语从句。
1. The fact ____ she works hard is well known to us all.
A. that B. what C. why D. which
2. The fact ____ he was successful proves his ability.
A. hat B. what C. which D. why
3. The news ____ he was kidnapped surprised us greatly.
A. what B. that C. why D. when
4. His suggestion ____ the meeting be delayed was turned down.
A. which B. that C./ D. it
5. I have no idea ____ he will start.
A. when B. that C. what D./
6. I've come from the government with a message ____ the meeting won't be held tomorrow.
A. if B. that C. whether D. which
7. The thought ____ he might fail in the exam worried him.
A. when B. which C. what D. that
8. The order ____ the prisoner be set free arrived too late.
A. which B. whether C. that D. what
9. The nurses are trying their best to reduce the patient's fear ____ he would die of the disease.
A. that B. as C. of which D. which
10. He often asked me the question ____ the work was worth doing.
A. whether B. where C. that D. when
Keys: 1-5 AABBA 6-10 BDCAA
The possibility that the majority of the labour force will work at home is often discussed. (同位语从句)
We are not looking into the question whether he is worth trusting. (同位语从句)
Word came that he had been abroad. (同位语从句)
Our team has won the game, which made us very happy.
The doctor whom you are looking for is in the room.
His mother did all she could to help him with his study.他妈妈尽她的最大努力帮助他的学习?(定语从句,代词all作先行词?)
The news that our team has won the game was true. 我们队赢了那场比赛的消息是真的?(同位语从句,补充说明news到底是一个什么消息?)
The news that he told me yesterday was true. 昨天他告诉我的那个消息是真的?(定语从句,news在从句中作told的宾语?)
I made a promise that if anyone set me free I would make him very rich. 我许诺如果谁让我自由,我就让他非常富有?(同位语从句,补充说明promise到底是一个什么诺言?)
The mother made a promise that pleased all her children. 妈妈做出了一个令她的孩子们高兴的许诺?(定语从句,promise在从句中作pleased的主语?)
有些引导词如how, whether, what可以引导同位语从句,但不能引导定语从句?如:
That question whether we need it has not been considered. 我们是否需要它这个问题还没有考虑?(同位语从句)
I have no idea what has happened to him. 我不知道他发生了什么事?(同位语从句)
The order that we should send a few people to help the other groups was received yesterday. 我们应派几个人去帮别的几个小组的命令昨天收到了?(同位语从句,是对order的具体解释,that虽不作成分,但不能省略?)
The order that we received yesterday was that we should send a few people to help the other groups. 我们昨天收到的命令是我们应该派几个人去帮助别的几个小组?(定语从句,是名词order的修饰语,that在从句中作received的宾语,可以省略?)