名词性从句
在句子中起名词作用的句子叫名词性从句(Noun Clauses）。名词性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，因此根据它在句中不同的语法功能，名词从句又可分别称为主语从句、宾语从句、表语从句和同位语从句。
第一节知识点讲解
顾名思义，主语从句在句子中作主语。有时本身出现在主语的位置上，也有时出于句子结构的考虑退到句子的尾部，前面用形式主语it代替。从句作主语时，谓语动词一般为单数形式。如:
What I saw was beyond any verbal description.
That his hair was turning grey worried him a bit.
Why the company denied the contract is still unknown.
When and where the government will build a city square is under discussion.
It is pretty annoying that a small part of the machine is missing.
It remains to be seen whether the new novel will be well received.
Tips: 主语从句的that绝对不能省去。因为句子是不能做主语的，故用that引导。若去掉则没有了主语，而宾语从句的that可省。
主语从句：That he is right is known to all of us.
宾语从句：We all know (that) he is right.
1. It 作形式主语和it引导强调句的比较
It 作形式主语代替主语从句，主要是为了平衡句子结构，主语从句的连接词没有变化。而it引导的强调句则是对句子某一部分进行强调，无论强调的是什么成分，都可用连词that。被强调部分指人时也可用who/whom。例如：
a) It is a pity that you didn’t go to see the film. 你不去看那场电影真可惜。
b) It doesn’t interest me whether you succeed or not. 我对你成功与否不感兴趣。
c) It is in the morning that the murder took place. 谋杀案是在早上发生的。（强调句型）
d) It is John that broke the window. 是John打碎的窗户。（强调句型）
2. 用it 作形式主语的结构
(1) It is ＋名词＋从句
It is a fact that … 事实是…
It is an honor that …非常荣幸
It is common knowledge that …是常识
(2) It is ＋形容词＋从句
It is natural that… 很自然…
It is strange that… 奇怪的是…
(3) It is ＋不及物动词＋从句
It seems that… 似乎…
It happened that… 碰巧…
It appears that… 似乎…
(4) It ＋过去分词＋从句
It is reported that… 据报道…
It has been proved that… 已证实…
It is said that… 据说…
3. 主语从句不可位于句首的五种情况：
（1）if 引导的主语从句不可居于复合句句首。
（2）It is said /reported…结构中的主语从句不可提前。例如：
正确表达：It is said that President Jiang will visit our school next week.
错误表达：That President Jiang will visit our school next week is said.
（3）It happens/occurs…结构中的主语从句不可提前。例如：
正确表达：It occurred to him that he failed in the examination.
错误表达：That he failed in the examination occurred to him.
（4）It doesn’t matter how/whether …结构中的主语从句不可提前。例如：
正确表达：It doesn’t matter whether he is wrong or not.
错误表达：Whether he is wrong or not doesn’t matter.
（5）含主语从句的复合句是疑问句时，主语从句不可提前。例如：
正确表达：Is it likely that it will rain in the evening?
错误表达：Is that will rain in the evening likely?
4. what 与that 在引导主语从句时的区别
what 引导主语从句时在句时在从句中充当句子成分，如主语．宾语．表语，而that 则不然。例如：
a) What you said yesterday is right.
b) That she is still alive is a consolation
宾语从句就是在复合句中作宾语的名词性从句，通常放在主句谓语动词(及物动词) 或介词之后。
We assumed that there would be more than 100 guests.
He told the police in detail what he saw and heard.
Nobody is sure what humans will look like in a million years.
That will depend on whether they can get the chance.
Whether I will have the time I am not sure at the moment.
The conductor complained that we were not gifted in singing and that he would never come again.
1. 作动词的宾语
(1) 由that引导的宾语从句(that 通常可以省略), 例如：
I heard that be joined the army. 我听说他参军了。
