【同位语从句定义】同位语从句就是一个句子做同位语。常放在抽象名词后面，说明该名词的具体内容。换言之，同位语从句和它所解释所的名词在内容上是一致的，同做一个句子成分，仅仅是对其内容作进一步说明。

【哪些词可以带同位语从句】并不是所有的名词都可以带同位语从句，这就缩小了包围圈。只有某些可以包含同位语从句内容的抽象名词才可以带同位语从句。

【常见的可带同位语从句的抽象名词有】fact, news, idea, truth真理、真相, hope, problem, information信息、资料, wish,  promise承诺，答应, answer, evidence证据, report, explanation解释, suggestion建议, conclusion结论等

【能够引导同位语从句的引导词有】

1. that引导出一个陈述句

2.whether引导出一个带有“是否”的句子（不能用if）

3. 有疑问代词和疑问副词变来的引导词：what, which, who, when, where, why, how 等

【如何选择引导词】正确运用同位语从句的引导词，准确把握同位语从句

1.如同位语从句意义完整，应用that引导同位语从句。（即that 不充当任何成分，只起连接作用，不可省略）

　　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。

2.如同位语从句意义不完整，需增加"是否"的含义，应用whether引导同位语从句。（if不能引导同位语从句）

　　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。

【同位语从句一般紧跟先行词，也有分开的情况】当主句的谓语较短，而同位语从句较长时，同位语从句常后置。

如：The thought came to him that maybe the enemy had fled the city.   

【同位语从句和宾语从句的判别方法】

1.      同位语从句的先行词可以包括同位语从句的内容，该先行词不在从句中充当任何句子成分。在先行词与从句之间加上一个系动词be, 可以使之构成一个新句子，如果句子通顺且符合逻辑，则为同位语从句，反之，则为定语从句。

2.      定语从句中的先行词要在定语从句中从当一个句子成分，特别是宾语。定语从句只是对先行词的做限定，而不涉及到那个词所包含的内容。

3.      如果听到定语从句的先行词，你的好奇程度就很高，很想知道是什么内容，如果别人不想告诉你，你就不知道；反之，同位语从句会直接告诉你先行词的内容，没有秘密可言。

【例句与练习】

1.      This is the report that he wrote last night.(定语从句。report是write的宾语)

2.      The report that he is going to be the chairman of the board is not true. (同位语从句，解释了report的内容，可以改写成：The report is that he is going to be the chairman.)

3.      I didn’t know the news that he told you yesterday.

4.      I didn’t know the news that he had gone to Hong Kong.

5.      Who gave him the order that we should keep secret?

6.      Who gave you the order that we should withdraw?

7.      This is the message he left here just now.

8.      This is the message that he will not come back for dinner.

9.      I don’t know the truth that all of you know.

10.   I don’t know the truth that the woman beat the man first.

【巩固性练习】首先判断是什么从句， 再做题：

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. that    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