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[摘要]本文介紹了名词性从句的概念及运用，并针对学习过程中存在的问题进行了比较与区别，提出了注意点，帮助大家便捷、高效地掌握名词性从句。
[关键词]主语从句 宾语从句 表语从句 同位语从句
在句子中起名词作用的句子叫名词从句。名词从句的功能相当于名词词组，它在复合句中能担任主语、宾语、表语、同位语、介词宾语等。根据它在句中不同的语法功能，名词从句又可分为主语从句、宾语从句、表语从句和同位语从句。
一、 主语从句在句子中充当主语， 句子的谓语动词用第三人称单数
What he wants to tell us is not clear.
Who will win the match is still unknown.
有时为避免句子头重脚轻，常用形式主语it代替主语从句作形式主语放于句首，而把主语从句置于句末。主语从句后的谓语动词一般用单数形式。常用句型：形式主语it+谓语部分+主语从句
It is possible that Mary will come later.
It was a surprise that Tom did very well in the final exam.
在主语从句中用来表示惊奇、不相信、惋惜、理应如此等语气时，谓语动词要用虚拟语气“(should) +do”，常用的句型有：
It is necessary (important， natural， strange， etc.) that …
It is a pity (a shame， no wonder， etc.) that…
It is suggested (requested， proposed， desired， etc.) that…
二、宾语从句在句子中充当宾语， 从句用陈述句语序，一般放在及物动词或介词之后，宾语从句是名词性从句中的重点
（1）用作主句中及物动词的宾语，这类动词通常有：say，think,insist,hope,suppose,believe,agree,expect,explain,order,suggest,demand,feel,know,wonder,ask,realize等。例如：
We never doubt (that) he is honest.
Nobody can tell when she will arrive.
（2） 用作动词短语的宾语，如：
It depends on whether you can understand the text.
You must give it back to whomever it belongs to.
三、在句中作表语的从句叫表语从句，表语从句位于连系动词后，其基本结构为：主语 + 系动词 + that从句
It looks as if it is going to rain.
我们需要注意，当主语是reason时，表语从句要用that引导而不是because。
The reason why he was late was that he missed the train by one minute this morning.
连词that 引导表语从句时不能省略；连词if 不能引导表语从句，只能用whether.
The question is whether it is worth doing.
四、同位语从句是对与之同位的名词中心词作进一步解释, 说明其前面的名词的具体内容,在逻辑上表现为同位关系,同位语从句通常由that引导,能接同位语从句的常见名词有
idea, fact, news, promise ,suggestion,belief, hope, evidence, opinion, problem, truth, answer, proposal, theory, decision, discovery, problem, thought 等。
The news that we won the game is exciting.
同位语从句和定语从句都可由that 引导，在运用过程中常常会混淆，我们要学会区别：
that作为关系代词，可以引导定语从句，充当句子成分，在从句中作宾语时可以省略； that引导同位语从句时，起连词的作用，没有实际意义，不充当句子成分，一般不能省略。
试比较下面两个例句:
I had no idea that you were here．（that引导同位语从句，不能省略）
Have you got the idea（that）this book gives you of life in ancient Greece？（that引导定语从句，作宾语，可以省略）
五、引导名词性从句的连词在下列情况下是不可省略的，在学习和运用过程中要记住
1. 介词后的连词
2. 引导主语从句和同位语从句的连词不可省略。
That she was chosen made us very happy.
We heard the news that our team had won.
六、whether与if 均为"是否"的意思。 但在下列情况下，whether 不能被if 取代
1. whether引导主语从句并在句首
2. 引导表语从句
3. whether从句作介词宾语
4. 从句后有"or not"
5．后接动词不定式时
6.某些动词后面(如discuss) 只能用whether, 不用if。
Whether there is life on the moon is an interesting question.
The question is whether she should have a low opinion of the test?
Everything depends on whether we have enough money.
I wonder whether he will come or not.
Can you tell me whether to go or to stay?
[关键词]主语从句 宾语从句 表语从句 同位语从句
在句子中起名词作用的句子叫名词从句。名词从句的功能相当于名词词组，它在复合句中能担任主语、宾语、表语、同位语、介词宾语等。根据它在句中不同的语法功能，名词从句又可分为主语从句、宾语从句、表语从句和同位语从句。
一、 主语从句在句子中充当主语， 句子的谓语动词用第三人称单数
What he wants to tell us is not clear.
Who will win the match is still unknown.
有时为避免句子头重脚轻，常用形式主语it代替主语从句作形式主语放于句首，而把主语从句置于句末。主语从句后的谓语动词一般用单数形式。常用句型：形式主语it+谓语部分+主语从句
It is possible that Mary will come later.
It was a surprise that Tom did very well in the final exam.
在主语从句中用来表示惊奇、不相信、惋惜、理应如此等语气时，谓语动词要用虚拟语气“(should) +do”，常用的句型有：
It is necessary (important， natural， strange， etc.) that …
It is a pity (a shame， no wonder， etc.) that…
It is suggested (requested， proposed， desired， etc.) that…
二、宾语从句在句子中充当宾语， 从句用陈述句语序，一般放在及物动词或介词之后，宾语从句是名词性从句中的重点
（1）用作主句中及物动词的宾语，这类动词通常有：say，think,insist,hope,suppose,believe,agree,expect,explain,order,suggest,demand,feel,know,wonder,ask,realize等。例如：
We never doubt (that) he is honest.
Nobody can tell when she will arrive.
（2） 用作动词短语的宾语，如：
It depends on whether you can understand the text.
You must give it back to whomever it belongs to.
三、在句中作表语的从句叫表语从句，表语从句位于连系动词后，其基本结构为：主语 + 系动词 + that从句
It looks as if it is going to rain.
我们需要注意，当主语是reason时，表语从句要用that引导而不是because。
The reason why he was late was that he missed the train by one minute this morning.
连词that 引导表语从句时不能省略；连词if 不能引导表语从句，只能用whether.
The question is whether it is worth doing.
四、同位语从句是对与之同位的名词中心词作进一步解释, 说明其前面的名词的具体内容,在逻辑上表现为同位关系,同位语从句通常由that引导,能接同位语从句的常见名词有
idea, fact, news, promise ,suggestion,belief, hope, evidence, opinion, problem, truth, answer, proposal, theory, decision, discovery, problem, thought 等。
The news that we won the game is exciting.
同位语从句和定语从句都可由that 引导，在运用过程中常常会混淆，我们要学会区别：
that作为关系代词，可以引导定语从句，充当句子成分，在从句中作宾语时可以省略； that引导同位语从句时，起连词的作用，没有实际意义，不充当句子成分，一般不能省略。
试比较下面两个例句:
I had no idea that you were here．（that引导同位语从句，不能省略）
Have you got the idea（that）this book gives you of life in ancient Greece？（that引导定语从句，作宾语，可以省略）
五、引导名词性从句的连词在下列情况下是不可省略的，在学习和运用过程中要记住
1. 介词后的连词
2. 引导主语从句和同位语从句的连词不可省略。
That she was chosen made us very happy.
We heard the news that our team had won.
六、whether与if 均为"是否"的意思。 但在下列情况下，whether 不能被if 取代
1. whether引导主语从句并在句首
2. 引导表语从句
3. whether从句作介词宾语
4. 从句后有"or not"
5．后接动词不定式时
6.某些动词后面(如discuss) 只能用whether, 不用if。
Whether there is life on the moon is an interesting question.
The question is whether she should have a low opinion of the test?
Everything depends on whether we have enough money.
I wonder whether he will come or not.
Can you tell me whether to go or to stay?