名词性从句的连接词有从属连词that/whether/if，

连接代词what/who/which/whose/whatever/whoever/whomever/whichever，

连接副词where/when/why/how/wherever/whenever。

1.that的用法。

(1)主语从句、表语从句、同位语从句中用that但不能省略。

☞That they are good at English is known to us all.

☞The problem is that we don’t have enough money.

☞The report that there will be a severe storm in the northern area is false.

(2)一般情况下，宾语从句中的引导词that可省略，但在以下几种情况中that一般不省略：

①当that从句和主句谓语动词之间有插入语时；

②有多个that引导的从句时，第一个that可以省略，而其他的that常不可省略；

③介词except，but，besides，in等后跟that引导的宾语从句时；

④当when，who，what，where，why，how等引导的从句与that引导的从句作主句谓语动词的并列宾语时。

☞He judged that，because he was a child，he did not understand wine.

☞The reason lies in that she works harder than the others do.

☞Everyone knew what happened and that she was worried.

(3)that和what的区别。

that 引导名词性从句时，在主从句中不担当任何句子成分，也没有任何含义；而what引导名词性从句时，在主从句中都要充当一定的句子成分，what可以分解成定语从句中的＂先行词＋关系代词＂，即常说的＂先行词＋that＂。

☞It’s a shame that he has made such a mistake.

☞I will do what I can (do) to help him.

(4)同位语从句与定语从句中that的区别。

同位语从句中的连接词that只起连接作用，在从句中不担当任何句子成分；而定语从句中的关系代词that在句中作宾语或主语，与先行词有修饰关系。如果句子

是同位语从句，就应用连接词that而不能用which。同位语从句一般放在表具体含义的名词后解释说明名词的含义或内容，如以下名词：news，fact，suggestion，truth，plan，belief，doubt，possibility，idea等，而定语从句只是对先行词的限定和修饰。

☞They expressed the hope that they would come to visit China again.(同位语从句)

☞The hope they expressed is that they would come to visit China again.(定语从句)

2.whether和if的用法。

☞ (1)whether和if在宾语从句中可以互换，但是作介词宾语时连接词一般用whether。

It all depends on whether they will come back.

(2)后面直接跟or not 时用whether。

☞I didn’t know whether or not he had arrived in Wuhan.

(3)主语从句、表语从句中只能用whether。

☞Whether the meeting will be put off has not been decided yet.

☞The question is whether they have so much money.

(4)whether可以引导同位语从句，用以说明前面的名词的内容，if则不能。

☞We ought to discuss carefully the question whether we can do it or not.

(5)whether常与or连用表示一种选择，if不能这样用；whether也可与动词不定式连用但if不能。

☞The question of whether they are male or female is not important.

☞I have not decided whether to go or not.

(6)间接宾语位于句首时或者间接宾语提前时用whether不用if。

☞Thank you，but whether I’ll be free I’m not sure at the moment.

(7)whether可引导一个让步状语从句表示＂不管＂、＂无论＂，而if不能。

☞Whether he comes or not，we will begin our party on time.

3.疑问词＋ever和no matter＋疑问词的区别。

(1)疑问词＋ever可引导名词性从句，在主从句中要充当一定的成分。

☞Whoever breaks the rule must be punished.

☞You can choose whatever you like in the shop.

(2)疑问词＋ever还可引导让步状语从句。

☞Whoever breaks the rule，he must be punished.

☞Whatever you do，you must do it well.

(3)no matter＋疑问词只能引导让步状语从句。

☞No matter what you do，you must put your heart into it.

☞No matter who comes late，he must be punished.

4.when和where引导的同位语从句与定语从句的区别。

when 和where前面的名词若是表示时间、地点的名词，则when和where引导的是定语从句，否则则为同位语从句。

☞They put forward the question where they could get the money.(同位语从句)

☞This is the place where the accident happened.(定语从句)

5.名词性从句中that不宜省略的几种情况

宾语从句或表语从句中that有时可以省略，但在以下情况时，that不宜省略。

（1）当动词后带有两个并列的宾语从句时，引入第二个从句的连词that不可省略。如：

The teacher told the students (that) they should hand in their homework the next day and that the homework must be signed names by their parents.

老师告诉学生他们要在第二天交上作业，并且作业必须由家长签名。

（2）当that前面有插入语时，that不宜省略。如：

Little Alice didn't know, I'm sure, that her sister was going to America.

我确信，小艾丽斯不知道她的姐姐很快就要去美国了。

（3）省略答语中，that宾语从句单独出现时，that不可省略。如：

—What did he say? 他说了什么

—That he would visit the Great Wall. (他说)他将会参观长城。

（4）当主句的状语部分位于that 宾语从句之前时，that不宜省略。如：

Jane realized at once that she must do with it herself. 珍立刻意识到她必须亲自处理那件事。(如省略that，at once也可能修饰从句，是表示＂立刻意识到……＂，还是表示＂立刻去处理……＂，较为含糊)

（5） 当that 宾语从句中的状语部分位于从句的前部时，that不宜省略。如：

☞Tom promised that if he could earn as much as 500 dollars in this month, he would buy a computer for his brother. 汤姆许下诺言，如果他在这个月里能够赚到500美元，他就给他的弟弟买台电脑。

（6）当that 宾语从句是双宾语中的直接宾语时，that一般不宜省略。如：

☞I will never tell anyone that you have ever been there.

我绝对不会告诉别人你曾经去过那儿。

（7）当为了强调而把that引导的主语从句位于句首时，that不可省略。如：

That they would take the risk was very clear. 他们将要冒这个险是很清楚的了。

（8）当主句中的谓语动词是固定词组时，其宾语that从句中的 that 不宜省略。如：

☞Mary has made up her mind that she will study hard for the scholarship, so she can have the chance to go abroad for further study.

玛丽下定决心努力学习以获得奖学金资格，这样她就有机会出国深造了。

（9）当that 宾语从句前有 it作其形式宾语时，that不可省略。如：

We think it important that college students should master at least one foreign language.

我们认为大学生至少掌握一门外语是很重要的。

（10）当引导同位语从句时，that一般不可省略，尤其当that与先行词处于分割情况时。如：

☞He heard the news that his team had won.

他听到了他的队获胜的消息。

☞There is a feeling in me that they are cheating me.

我有一种感觉他们在骗我。

（11）当that 宾语从句的主语是非谓语动词或是主语从句时，that不可省略。如：

The doctor said that taking exercise was the best way of losing weight.

医生说运动是最好的减肥方式。