在复合句中起名词作用的从句叫做名词性从句。名词性从句主语从句 表语从句 宾语从句 同位语从句 连接代词 who, whom, whose, which, what, whatever连接副词 how, why, when, where however, wherever连接词that, whether, if, becauseas if /as though （不充当从句的任何成分） 引导名词性从句的关联词在名词性从句中一律用陈述句的语序，即使从句表达的是疑问含义。 The problem is what he has done to the little boy. 问题是他对那个小男孩做了些什么。 1. 主语从句在句中作主语的句子叫主语从句。 主语从句通常由从属连词 that ，whether 和连接代词 what, who, which, whatever, whoever 以及连接副词 how,when,where, why等词引导。 that 在从句中无词义，只起连接作用；连接代词和连接副词在句中既保留自己的疑问含义、又起连接作用，在从句中充当成分。 What he wants to tell us is not clear. 他要跟我们说什么，还不清楚。Who will win the match is still unknown. Where the English evening will be held has not yet been announced. That he stole a bike was true. 单个的主语从句作主语时，谓语动词用单数形式。如果是两个或两个以上的主语从句作主语，谓语动词则用复数形式。 Where and when he was born has not been found. When the person was murdered and why he was murdered are still unknown. 有时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。主句的谓语动词一般用单数形式。常用句型如下：1 ） It + be + 名词 + that 从句2 ） It + be + 形容词 + that 从句 3 ） It + be + 动词的过去分词 + that 从句4 ） It + 不及物动词 + that 从句It is known to us how he became a writer. 我们都知道他是如何成为一名作家的。It is a pity that… it’s a shame that… It’s no wonder that…It is suggested that…It’s requested that…It’s proposed that…, It’s desired that…注意 : 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 It’s important, It’s naturalst...
