高中英语语法详解（讲义）chapter 7
主语从句和表语从句
一、主语从句
■一、名词性从句
■二、主语从句
■三、主语从句的位置
■四、名词性从句中的引导词
一、名词性从句
在复合句中，从句可作主语、表语、宾语、同位语、定语和状语
等。因此，复合句可分为：主语从句、表语从句、宾语从句、同位
语从句、定语从句和状语从句。
主语从句、表语从句和宾语从句在复合句中所起的作用跟名词相
同，所以又可称为名词性从句。这三种从句有下列相同之处：
1．关联词相同。
（a）从属连词——that, whether, if。
（b）疑问代词——除起连接作用外，还可以在从句中作主语、
宾语、定语等，有who (whom, whose), what, which。
（c）疑问副词——除起连接作用外，还在从句中作状语，有
when, where, how, why。
2．从句不能用逗号跟主句分开。
3．连词that无意义。
【说明】1．连词if作“是否”解时，引导宾语从句。
2．疑问代词、疑问副词常保留疑问的意义（另一情况却作
“（所）……的东西、事情”解）。
它们引导的从句与疑问词起句的特殊疑问句的语序不同：从句仍
用陈述句的语序。
二、主语从句
主语从句在句中作主语，它的位置跟陈述句基本结构中的主语相
同。它通常由从属连词（that, whether, if）、疑问代词（who, what,
which）、疑问副词（when, where, how, why）等引导。例如：
What you foresaw has happened.你所预料的事终于发生了。
Whether they do it or no matters little to us.他们是否做这件事， 跟
我们关系极小。
Who set the new record has not been found out.谁创造了新纪录尚未
弄清楚。
Whoever says that is wrong.无论谁那么说都是错误的。
Which of these two plans is better remains to be seen.这两个计划中
哪一个好些还得看一看。
When he will return is the important question.重要的问题是他什么
时候回来。
Where you get drinking water depends on where you live.你在什么
地方取得饮用水就看你住在哪里。
Why they are reducing price does not matter.他们为什么减价并不重要。
that引导的主语从句置于句首时，that不能省略。例如：
①That we are invited to a party this evening is a good news to us.我
们被邀请参加今晚的晚会，这对我们来说是个好消息。
whether 导引导的主语从句如果置于句首，whether 不能用 if 代
替。
②Whether there is life on the moon is no longer a question.月球是否
有生命不再是个问题了。
主语从句放在句首，句子常常显得笨重，因此常把它移到句末，
句首用引导词 it 作形式主语。上述①、②例句可改为下面③、④例
句：
③It is a good news to us (that) we are invited to a party this evening.
④It is no longer a question whether there is life on the moon.
that 引导的主语从句在用 it 作形式主语的结构中，that 可省略，
如上述第③例句。又如：
It seems unlikely (that) she will refuse the order.似乎她不可能 会拒
绝命令。
whether 引导的主语从句既可位于句首，也可位于主句之后，如
上述例子；若用if引导，只能位于主句之后。例如：
It is uncertain if he will come.他是否会来还不一定。
三、主语从句的位置
主语从句可以放在句首，也可放在句末。（一）it作形式主语
1．全句如是一般疑问句，多用 it 作形式主语以使句子保持平
衡。例如：
Isn't it strange that he should have left without telling us?他没有告诉
我们就走了，不是很奇怪吗？
Isn't it amazing that so many passengers were unhurt in the accident?
在这次事故中，这么多乘客没受伤，这不是使人感到惊奇吗？
2．句子是感叹句，必须用it作形式主语的结构。例如：
How strange it is that the children are so quiet！真奇怪，孩子们这
么安静！
3．“It be＋过去分词＋主语从句”结构。
这种结构中的 It是形式主语；主语从句多用 that引导，也可用其
他关联词引导。常见的过去分词有：
It be thought that…有人认
It be said that…据说
为
It be reported that…据报道 It be recorded that…据记载
It be expected that…预期 It be estimated that…据估计
It be asserted that…有人声称 It be assumed that…假设
It be known that…大家知道 It be noted that…有人指出
It be accepted that…人们公认 It be agreed that…一致认为
It be stressed that…人们强
It be found that…人们发现
调说
It be proposed that…有人建
It be proved that…已经证明
议
It be announced that…（有人）宣
布
It be decided that…已经决定
It is known to all that the Pacific is the largest of the four oceans.大家
都知道太平洋是四大洋中最大的。It should be pointed out that this accident could have been avoided.应
当指出，这个事故本来是可以避免的。
It was once thought that lead could be changed into gold.从前人们认
为，铅能够变成金。
It has been decided that production should begin in a few months.已
经决定，几个月后即开始生产。
4．“It＋不及物动词＋主语从句”结构。
这种结构中，It 是形式主语；主语从句多用 that引导。常见的不
及物动词有 seem, appear, occur, happen, strike, matter, chance, turn out,
(thus) come about等。例如：
It seems that everything in the universe is energy.看来宇宙的一切都
是能量。
It appears to me that there is something wrong with the engine.我看
发动机有点毛病。
It seldom happens that any felicity comes so pure as not to be
tempered and alloyed by some mixture of sorrow.（Cervantes）任何幸
福总不会十分纯粹，多少会掺杂一些悲哀。
It occurred to me that perhaps he was trying to shield someone.我想
他也许在设法庇护某人。
5．“It be＋名词＋主语从句”结构。
这种结构中，It 是形式主语；主语从句多用 that引导，也可用其
他关联词引导。常用的名词有 fact, news, question, matter, thing,knowledge, use, pity, case, wonder, mystery, secret, sense, practice 等。
例如：
It is common knowledge that machines make our work easier.人所共
知，机器能使我们工作容易些。
It is odds that he will come.他大概会来。
It is no wonder that the new technique will enable us to get better
results.毫不奇怪，新技术将使我们得到更好的效果。
It is a well-known fact that the moon has no light of its own.月球本身
不会发光，这是众所周知的事实。
It's his own affair where he goes on Sundays.星期天他去什么地方是
他个人的事。
6．“It be＋形容词＋主语从句”结构。
这种结构中，It 是形式主语；主语从句多用 that引导，也可用其
他关联词引导。常用的形容词有：apparent, appropriate, certain, clear,
conceivable, curious, desirable, disappointing, doubtful, essential,
evident, fortunate, important等。例如：
It is obvious that theory comes from practice.显然，理论来自实验。
It is quite evident that that country is facing a grave economic crisis.
很明显，该国正在面临严重的经济危机。
It is clear that waves are largely caused by winds.波浪显然是由风引
起的。
It is immaterial where or when he goes.他去哪里或什么时候去，都无关紧要。
It were not best that we should all think alike; it is difference of
opinion that makes horse races.（Mark Twain）使大家的思想都一样，
并非最善之策；赛马之所以能够举行，就是由于人们有不同的想
法。
It is still open to question who is to head the group.谁领导这个小组
还没有肯定。
在这种句型中，如果主句的表语是 necessary, desirable, important,
essential, advisable, odd, surprising, amazing, ridiculous 等形容词时，
主语从句的谓语常用“should＋原形动词”型虚拟语气，should常可
省略。例如：
It is advisable that everyone should have a map.最好是每人都应该
有一张地图。
It is essential that remote control (should) be introduced into the
system.重要的是，这个系统应采用遥控。
It is desirable that these heat losses (should) be reduced as far as
possible.最好使这些热量尽量减少。
（二）不能用it作先行词
名词性关联词引导的主语从句（也就是说，主语从句表示具体事
物或人、具体时间或地点时）只能位于句首，不能用 it 作先行词。
例如：
What I found, I think, was a wild iris.（James J.Kilpatrick）我想，我所发现的是一棵野生的蝴蝶花罢了。
Whichever device he is going to use is no matter.无论他用哪一个装
置都不要紧。
Whoever violates the regulations shall be punished.破坏规章的人必
将受到惩罚。
Where he went was Beijing.他去的地方是北京。
A good style should show no sign of effort.What is written should
seem a happy accident.（Maugham）好的文体应该没有斧凿痕迹。所
写的东西应该是神来之笔。
四、名词性从句中的引导词
名词从句中的 wh-词可能用作疑问词，也可能用作名词性关 联
词。
（一）用作疑问词
保留疑问词义，在句中担任一个成分，有 what, which, who,
whom, when, where, why 和 how.（另外，whether 和 if 有词义，但在
句中不担任成分）例如：
What laser is is clear to us now.激光是什么，我们现在明白了。
What type of exercises one should choose depends upon one physical
condition.一个人应该选择什么样的运动，取决于他的身体情况。
When men first made use of electricity is not exactly known.人类何
时首先使用电还不完全清楚。
Where cosmic rays come from still remains a puzzle.宇宙射线来自何处，仍然是个谜。
（二）用作名词性关联词
这类词的含义是“先行词＋另一个关系代词或关系副词”，即表
示某一具体的事物、人、地点、时间或方法。比如：what=the
thing(s) that/which"……的事物／东西”；where=the place where"
……的地方”；when=the time when" ……的时候”；why=the reason
why"……的原因”；其余类推。它们已经失去了疑问意义。这类词
有 what, whatever, who, whoever, whom, whomever, which, whichever,
when, where, why, how等。例如：
What you have done to me is terrible！您对我所做的太可怕了！
What we anticipate seldom occurs; what we least expected generally
happens.（Disraeli）我们期望的事很少实现，我们最不希望的事往
往发生。
Who is not for us is against us.不赞成我们的人就是反对我们 的
人。
Where he has surpassed every other English writer is in his ballads
and songs.他超过英国的其他作家之处在于民歌和歌谣。
Science is what we are badly in need of.科学是我们迫切需要的。
He is not who he seems to be.他不是表面上看来那样的人。
The darkest hour in any man's life is when he sits down to plan how
to get money without earning it.人生最黑暗的时刻，就是坐下来谋划
不费劳力以获得金钱之时。He says customers should get what they pay for.他说顾客支付多少
钱就应该得到多少东西。
Charge customers exactly what the service costs them.向顾客收取服
务所值的费用。
We can and we will do what we long to do.我们能够而且决心做自
己想做的事。
二、表语从句
■一、用从属连词that,whether引导
■二、用连接代词who, whom, what, which引导
■三、用连接副词where, when, why, how引导
■四、用as if, as though, as, because引导
表语从句在句中作表语，它位于主句中的系动词之后。表语从句
所用的关联词跟主语从句相同，即用 that, whether, who, what, which,
where, when, why, how等引导。表语从句中的that通常不省略。
一、用从属连词that, whether引导
The fact is that everything in the universe is in constant movement.事
实是宇宙中的一切东西都处在不断运动中。
Your greatest fault is that you are careless.你最大的毛病是粗心。
What must astonish you is that these products are inferior and their
prices are high as well.使你感到吃惊的是这些产品质量低劣，而且价
钱又高。
The thing to be settled on now is whether anything can be done tosave him.现在要决定的事是：是否有办法拯救他。
What we want to know is whether the weight of a proton is much
greater than that of an electron.我们想知道的是质子的重量是否比电子
的大得多。
二、用连接代词who, whom, what, which引导
My question is who can make use of the new method to treat the
patient.我的问题是谁能使用这个新法治疗病人。
Love is what links two souls.（Green）爱是连接两个灵魂的纽带。
Gravity is what makes you weigh what you weigh.引力使我们称得
现在的重量。
The reality is not exactly what the song started out to be…现实并不
像这首歌开头所说的那样……
A man's own manner and character is what most becomes him.
（Cicero）人是由自己的风度和品质构成的。
The question is which test we should do first.问题是我们首先应该做
哪一个实验。
三、用连接副词where, when, why, how引导
This is where we differ.这就是我们存在分歧之处。
The part of the pencil which is under the water seems to be where it is
not.铅笔在水中的那一截，似乎不在原来的地方。
What I want to know is when the broadcasting English class begins
every morning.我想知道的事就是英语广播每天早晨什么时候开始。April is when the lilacs bloom.四月是丁香花开放的季节。
That is why we cannot love in the common sense.那就是我们不能像
普通人那样去相爱的原因。
That's why he found most young women unattractive, regardless of
their exterior beauty.那就是他觉得许多最年轻的女人尽管外貌很美，
但她们并无吸引力的原因。
This is how it was, is now, and ever shall be, the world without end.
（James J.Kilpatrick）世界过去如此，现在如此，将来也永远如此，
这就是它永无终期的原因。
The test of a man or woman's breeding is how they behave in a
quarrel.（George B.Shaw）检验一个男人或女人教养如何，就是看他
们发生口角时的表现。
四、用as if, as though, as, because引导
Some of the non-metals may look as if they were metals.有些非金属
看起来可能像金属一样。
The patient looks as if he had been ill for a long time.这个病人看上
去似乎病了很久似的。
Things are not always as they seem to be.事物并不总是像它看来的
那个样子。
Everything was just as we had left it.一切正像我们原来留下的那个
样子。
It may be as you say.这也许是像你说的那样。The telegram he sent is as follows.他发来的电文如下。
When a woman marries again it is because she detested her first
husband.（Oscar Wilde）女人再婚，是因为厌恶第一任丈夫。
有些句子由“This fact is…”，“The reason is…”“My idea is…”等
开始时，在非正式文件中可以省略连词that。例如：
The fact is the instrument is not in good condition.事实是仪器出了
故障。
The reason is metals have many particular properties.原因在于金属
有许多特性。
但若句子结构比较复杂，则that不可省略：
The energy debate is really just beginning.The only thing that is
certain is that anybody who makes firm predictions about future will be in
some part wrong.能源的争论才刚刚开始。只有一件事是肯定的，那
就是对未来作坚定预言的任何人不会完全是对的。
主句中的主语如果是一些表示“建议”、“要求”或“命令”等
名 词 如 suggestion, proposal, resolution, idea, motion, requirement,
command, desire, wish, advice 时，则表语从句的谓语用虚拟语气，即
“should＋动词原形”，should常省略。例如：
My suggestion is that we (should) treat the patient with Chinese
medicine.我的建议是我们应该用中药治疗这个病人。
The judge's order is that the case (should) be investigated again.法官
的命令是此案要重新调查。当主句中主语的谓语是由 look, seem, sound, smell, taste, appear
等系动词表示时，由 as if, as though 引导的表语从句，如果表示“可
能性大”，用陈述语气；如果表示“可能性不大，强调假设”，用
虚拟语气。例如：
It looks as if it is (were) going to rain.好像天要下雨。
It sounds as if somebody is (were) knocking at the door.好像有人正
在敲门。
