主语从句语法总结

主语从句语法总结
主语从句知识点总结：
⼀，主语从句的定义：在句中充当主语的从句。

⼆，主语从句的引导词：
连接代词：
注意：由that 引导的主语从句，有时为了使句⼦结构平衡，避免“头重脚轻”，常⽤it作形式主语，⽽把从句放后⾯。

例：That students should hard work is necessary.
改为it作形式主语：It is necessary that students should hard work.
构成⼀些常⽤句型：
1）It is + n.（名词）+从句
It is a pity/shame that... 遗憾的是....
It is a surprise that... 令⼈惊奇的是...
It is a fact that... ..是事实
It is common knowledge that... …..是常识
例句：It is a pity that(很遗憾)we lost the match.
It is a fact that(这是事实）he cheated in the exam.
2) It is + adj.（形容词）+从句
It's certain that... 肯定...
It is possible that... 很可能.....
It is unlikely that... 不可能....
It is obvious that... 很明显...
It is necessary \important \natural\...that...+(should) +do...
例句：It is possible that （很可能）she will come back tomorrow.
It is obvious that (很明显)this measure is effective.
3）lt+ be + 动词的过去分词+ that从句
4）lt+ be + 不及物动词+ that从句
三，主语从句的⽤法规则：
规则⼀：
主语从句中使⽤陈述语序。

即主语在前，谓语在后。

例：When he will come is not known.
规则⼆：
主语从句中是主谓⼀致关系，谓语动词⽤单数，取决于所跟的表语。

例：What I want is water.
What I want are apples.
规则三：
That 在主语从句中不能省略。

规则四：
引导主语从句在句⾸只能⽤whether，有it作形式主语的whether/if都可以.
四，主语从句------学法指导
依据“缺什么补什么”原则确定正确的连词。

所谓“缺什么补什么”是指从句与连词之间关系。

如果句⼦中缺主语，指⼈⽤who，指物⽤what；
如缺宾语，指⼈⽤whom，指物⽤what;
如缺时间状语⽤when; 地点状语⽤where; 原因状语⽤why; ⽅式状语⽤how；定语⽤what或which;什么都不缺⽤that. Wether表“是否”。