文档介绍：名词性从句相关知识点复****br/>一、 主语从句：英语中用作主语的从句就叫主语从句。
主语从句的引导词：
连词：that、whether> if
连接代词：who、whom、whose> what、which
连接副词： when> where> why、how
复合词：whoever> whomever> whatever> whichever
whether> if引导主语从句的区别：
主语从句置于句首时只用whether.
Whether he will come here is not decided yet.
当用it作形式主语，主语从句置于句中时，whether/if都可以。
It is unknown whether/if she will come today.
what引导的主语从句一般放在句首，谓语动词的单复数取决于主句中作表语的名词。
What we need is more time.
What they need are more English books.
连接副词when、where> why> how引导主语从句，既可以出现在句首，也可以用it作形 式主语。
Why Tom was late is still unknown.
It is quite clear why he did it.
连词that的用法：
Cl) that在句中无词义，只起连接作用，放在句首时，不能省略。
That he will come to the meeting is certain.
(2)为避免句子头重脚轻，常用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，常用句式：
be+n+that 从句
It is a pity that he can't come to my birthday party.
be + adj + that 从句
It is quite clear that the whole project will fail.
It be +及物动词过去分词+that从句
It is ordered that we (should) get everything ready this evening.
It +不及物动词+ that从句
It happened that I didn't take any money with me.
5 .单个的主语从句表示单一概念时，谓语要用单数形式。
What he wants to tell us is not clear.
主语为两个并列的主语从句时，谓语用复数形式。
When they will start and where they will go have not been decided yet.
两个并列连词连接一个主语从句时，谓语用单数形式。
When and where the meeting will begin has not been decided.
二、 同位语从句：英语中用作同位语的从句就叫同位语从句，位于一名词之后，用以解释说
明该名词的具体内容。
(一、)常见的同位语从句一般由that引导：
可由 that 引导同位语从句的名词有：ad