名词性从句
名词性从句（Noun Clause）在句子中起名词作用，根据它们在句中所起的语法作用，这类从句又可分别称为主语从句、表语从句、宾语从句、同位语从句和形容词补语从句。由于名词从句和名词作用相同，因此，可用作句子的主语、表语、宾语和介词宾语等。
1. 主语从句
(1) that引导的主语从句
that 引导的主语从句可以位于句首， 而常见的形式是将作形式主语用的先行词 it 置于句首。
That he will come to the discussion is certain.
他来参加讨论是肯定无疑的。
That mathematics is one of the most useful and fascinating divisions in human knowledge is widely accepted.
数学是人类知识中最有用和最令人着迷的部分之一，这一点受到了广泛的认可。
It is strange that she did not come yesterday.
很奇怪，她昨天没有来。
It is a pity that Mr Brown can't attend our English meeting. 真可惜，布朗先生不能出席我们的英语晚会。
(2) 连接代词和连接副词以及连接词 whether 引导的主语从句
Whether it will do us harm or good remains to be seen.
这事会对我们有害还是有益，还要等等看。
Where we shall do the test is still under discussion.
我们在什么地方做这个实验还在讨论。
Why the sun in the morning looks bigger than the sun at noon is very interesting.
为什么早晨的太阳看上去比中午的太阳大，这事很有趣。
疑问词引导的主语从句可以位于句首，也可以借助于先行词 it 后置。如：
Whether or not an object floats depends on the density of both the object and the water.
一个物体是否会浮起，既取决于该物体的密度，又取决于水的密度。
(3) 名词性关系代词what， whatever， whichever， whoever引导的主语从句。
Whoever breaks this law deserves a fine.
违反本法者应予以罚款。
Whichever (of you) comes in first will receive a prize.
(你们中)谁先来谁得奖。
What one thinks and feels is mainly due to tradition, habit and education.
一个人的思想和感情主要归因于传统、习惯和教育。(What=the thing which/that)
2. 表语从句
(1) that引导的表语从句
My idea is that you should make good use of your time.
我的建议是你该好好利用你的时间。
The reason Tom failed in the exam was that he didn't work hard.
汤姆考试没过的原因是学习不努力。
(2) 连接代词和连接副词以及连接词 whether 引导的表语从句
The question is whether we can finish our work by tomorrow evening.
问题在于我们能不能在明天晚上以前完成这项工作。
(引导表语从句的whether不能换作if）
That is why she had a day –off yesterday.
那就是她昨天请假的原因。
(3) as if 等引导的表语从句
It looks as if it is going to rain.
看起来天要下雨。
I felt as though my head were splitting.
我觉得头仿佛要裂开似的。
注：除了as if/as though之外，从属连词 as 和 because 也可以引导表语从句。
Things are not always as they seem to be.
事情并不总是如其表象。
It may be because he is too busy.
这可能是因为他太年轻了。
It is because he doesn't know hers.
这是由于他不认识她。
3. 宾语从句
(1) that引导的宾语从句
I know that he is friendly and hospitable.
我知道他很友好而且好客。
(由连接代词引导）
Almost all economists agree that nations gain by trading with one another.
几乎所有的经济学家都承认，各国在相互的贸易中受益。
注：
① they told us once again that the situation was serious.
他告诉我们说形势是严重的。
(亦可以说They told us that once again that the situation was serious.)
(他们告诉我们说形势又严重了)
但是两句中的that皆不可以省去，否则会产生歧义。
② He said he couldn't tell you right away and that you wouldn't understand.
他说他不能马上告诉你，你是不会理解的。
(said 之后可以省去that，但第二个that 不可省去。)
③ That he ever said such a thing I simply don't believe.
我简直不相信他曾说过这样的话。(that 从句置于句首是，that 不可省去)
④ We decided, in view of his special circumstances, that we would admit him for a probationary period.
鉴于他的特殊情况，我们决定给他一段试用期。
(2) 连接代词、连接副词以及连接词 whether/if 引导的宾语从句
History linguists study how languages evolve over time.
历史语言学家研究语言是如何随着时间的推移而发展的。(由连接副词引导)
Do you know when we shall have a meeting?
你知道我们什么时候开会吗？(由连接副词引导)
I asked him if he sure what he is doing.
我问他是否确信知道自己在做什么 ？(连接词if以及连接代词引导)
The teacher asked me whether or not I finished my work?
老师问我是否完成了作业。(连接词whether引导)
(3) 名词性关系代词 what, whatever, whichever, whoever 引导的宾语从句
He gave whoever asked for it a copy of his latest paper.
不论谁要他都将他最近写的论文给他一份。
The President is determined to resist what he regards as blackmail by the terrorists.
总统决心抵制他所认为的恐怖分子的敲诈。
You can call me whatever you like.
你叫我什么都行。
You may choose which appeals to you.
你对哪个感兴趣就可以选哪个。
Use which method you prefer.
你喜欢哪个方法就用哪个方法。
4. 介词宾语从句
(1) that引导的介词宾语从句
that引导的介词宾语从句仅限于用在 except, but, not with standing 等少数介词后。
His account is correct except that some details are omitted.
除了有些细节未提到外，他的叙述是正确的。
He would have helped us but that he was short of money at the time.
要不是他那时缺钱，他一定会帮助我们的。
(2) 连接代词和连接副词引导的介词宾语从句
I have no definite information yet as to which route he will take.
对他将走哪条路线，我们还没有确切的情报。
I know nothing about the matter except what you told me.
除你告诉我的情况以外，对此事我一无所知。
但要注意：引导介词宾语从句的 whether 不能换作 if 。
(3) 名词性关系代词 what, whatever, whichever, whoever 引导的介词宾语从句
The boy was interested in whatever he saw here.
那孩子对在那里看到的任何事物都感兴趣。
The first prize should go to whoever writes best.
头等奖应颁给最优秀的作者。
5. 同位语从句
(1) that 引导的同位语从句
We are very excited at the news that our Chinese athletes won many gold medals.
听到我们中国运动员赢得了许多金牌的消息我们非常激动。
A new idea occurred to him that it could be done in a very simple way.
他想出一个新主意：这件事可以用一种很简单的方法完成。
(2) 连接代词和连接副词引导的同位语从句
同位语从句通常由 that 引导，但随着与其同位的名词的不同，也可由 whether, when, which, who, how, what, why 等引出。如：
The question, whether we need it, has not yet been considered.
我们是否需要它，这个问题还没有被考虑。
I have no idea when she will be back.
我不知道她何时回来。
I have no idea which dictionary is hers.
我不知道哪本词典是她的。
(3) 同位语从句的位置
同位语从句有时不是紧跟在有关的名词后面，而是被其他的词隔开了。如：
We've just heard a warming on the radio that a typhoon may be on its way.
我们刚从广播里听到一则气象警报，说有一股台风即将到来。
The question came up at the meeting whether we had enough money for our research.
会上提出了我们的研究经费是否够的问题。
6. 形容词补语从句
(1) that引导的形容词补语从句
We are certain that he will get over his illness.
我们相信他会康复的。
Ralph was disappointed that he didn't finish the work on time.
拉尔夫没有按时完成工作，感到很失望。
但要注意：引导形容词补语从句的that可以省略。
(2) 连接代词、连接副词和连接词whether引导的形容词补语从句
I'm not certain whether the train will arrive on time.
我没有把握火车是否会准点到达。
The beggar was too sleepy to be aware how cold it was.
这个 乞丐太困了，没意识到天气有多冷。