名词性从句，语法书把它讲得繁琐而复杂。尤其是各种各样的引导词，什么“从属连词”啊，“连接代词”啊，“连接副词”啊，等等，英语初学者往往记不住甚至混淆不清。其实，只要我们把它们进行归类、对比，就发现名词性从句有规律可循。
顾名思义，名词性从句就是具有名词作用的从句。因为它在句中可以作主语、宾语、表语和同位语，所以又分为：主语从句，宾语从句，表语从句和同位语从句四种。其实，我们换个角度来看，名词性从句一点也不复杂。
名词性从句，我们先不考虑它们用何种引导词来引导。我们只考虑，这些句子如果是简单句的话，它们是些什么样的句子?原来就是我们学过的陈述句、一般疑问句和特殊疑问句啊。因此我们要记住：陈述句用that引导，一般疑问句用whether引导，特殊疑问句用特殊疑问词(即wh-word)引导。这样，基本问题就解决了。下面我们用3组例句进行讲解，每组例句都分别包含一个主语从句，宾语从句，表语从句和同位语从句，这样归纳看起来是很有意思的。
(一)that引导的各种名词性从句
1. That our team had won the match made us excited.
2. The headmaster said that our team had won the match.
3. The fact was that our team had won the match.
4. The headmaster announced the news that our team had won the match.
【特别提示】
在本组句子中，每句都含有that our team had won the match. 它在句1中作了句子的主语，是主语从句。在句2中作了said的宾语，是宾语从句。在句3中作了was的表语，是表语从句。在句4中作了news的同位语，是同位语从句。
1. that 引导的各种名词从句，都是陈述一个事实，没有疑问的含义。而且，that 只起引导作用，本身没有实际意义。
2. that 引导的主语从句，由于句子较长放在句首显得头重脚轻。为了使句子更加匀称，往往用it形式主语引导。例如：
It is clear that you have made a big mistake in your experiment.
It is a wonder that the wounded soldier is still alive.
3. that 引导的名词从句，在宾语从句中可以省略，但引导主语从句、表语从句和同位语从句时不可省略。偶尔引导表语从句时，口语中可以省略。例如：The truth is (that) I never been there.
4. 由于that 引导的各种名词从句，都是陈述一个事实。所以，无论是主语从句还是宾语从句、表语从句、同位语从句，其主句中并没有“悬而未决，带有疑问”的意思。因此，宾语从句经常和say, think, wish, hope, expect, suppose, see, believe, agree, explain, order, command, suggest, propose, insist, demand, require, declare, announce, know, hear, feel, imagine, notice, prefer, find, report, find out, regret, remember, forget, learn, decide, discover等词连用。同位语从句经常和fact, news, hope, truth, idea, suggestion, thought, promise, order, story, problem, belief, word, message, information, proof, announcement, desire, answer, proposal, advice, condition等名词连用。
(二)特殊疑问词引导的各种名词性从句
1. Who will attend the meeting has not been decided.
2. No one knows who will attend the meeting.
3. My question is who will attend the meeting.
4. The question who will attend the meeting remains to be discussed.
【特别提示】
在本组句子中，每句都含有who will attend the meeting. 它在句1中作了句子的主语，是主语从句。在句2中作了knows的宾语，是宾语从句。在句3中作了is的表语，是表语从句。在句4中作了question的同位语，是同位语从句。
1. 英语中有一种wh-word，也叫特殊疑问词，因为这些引导词都含有wh两个字母。它们是 who, whom, whose, whoever, what, whatever, which, when, where, how, why, 这些词均可引导四种名词性从句，并且这些引导词仍然具有疑问的含义。
2. 主语从句可以用形式主语it替代，而把主语从句置于句子的最后。如：
It has not been decided who will take the place of the manager.
It is still a question when we shall have our sports meet.
