一.概念：在句子中起名詞作用的句子叫名詞性從句。名詞性從句的功能相當於名詞詞組，他在複合句中能擔任主語、表語、賓語、同位語等因此根據它在句中不同的句法功能，名詞性從句共分為四種:主語從句,表語從句,賓語從句和同位語從句。
二.相關知識點精講
1． 主語從句：主語從句在整個句子中作主語。
(1)that不同於其它的連詞，它不充當句子的成分，只是單純的連接詞，通常不可以省略。分句置於句首時，that絕對不可以省略。
That the driver could not control his war was obvious.
It was obvious that the driver could not control his car.
(2)if 不能用在主語從句中，而是用whether。Whether引導的主語從句常置於句首。
Whether he left (or not) is unknown
(3)當主語從句作主語時，謂語動詞一般用第三人稱單數，下面這個句型例外。
What we need is more time and money. What we need are many more books.
2.表語從句：表語從句出現在系動詞後，充當表語。引導表語從句的連接詞主要有：that，whether，wh-類連接詞。
The trouble is that we are short of money. Go and get your coat. It’s where you left it.
(1) 引導表語從句除了上述三類詞外還有because
That’s because he didn’t understand me。It’s just because he doesn’t know her。
(2) as /as if/ as though也引導表語從句。此類表語從句常跟在特定的動詞後面，如「appear, look, seem，taste，sound，feel」等。
Things are not always as they seem to be。It sounds as if someone is knocking at the door。
At that time，it seemed as though I coundn’t think of the right word。
(3) 連繫動詞「appear, look, seem」的兩個常用句型
It seems/appears that….
It looks/seems as if/as though……(與事實相符用陳述語氣，與事實相反用虛擬語氣)
3. 賓語從句：及物動詞，形容詞和介詞後加賓語從句作其賓語。
(1) 賓語從句時態與主句相呼應，但賓語從句表示的是客觀真理或普遍現象除外
The teacher told us that the earth moves around the sun
(2) 連詞whether和 if引導賓語從句可以互換，但注意：
l 連詞後緊跟or not時用whether I want to know whether or not they will come.
l 作介詞賓語是用whether引導賓語從句 He was interested in whether he saw her there.
l 連接詞後直接加不定式，不能用if只能用whether
He doesn’t know whether to stay or not.
l 如果賓語從句是否定時，一般用if引導 I care if he will not attend the meeting.
(3) 當賓語從句後帶賓補時，要用「主語+謂語+it +賓補+that-clause, that不可省略
I think it certain that she will do well in her exam.
(4) 當主語是I, we ，主句用think, believe, suppose, expect, imagine五個動詞時，用否定轉移 I don’t think he will win the game, will he?
(5) that在賓語從句常可以省略，但由and或 but連接兩個或多個賓語從句時，僅可以省略第一個連詞that
He said (that) he had eaten nothing but that he wasn’t hungry.
(6) 注意區別if引導的賓語從句和條件狀語從句
I don’t know if he will come. If he comes, I』ll let you know.
4.同位語從句，在句中作某些名詞的同位語，對前面的名詞進一步說明。用在下列名詞 fact,news,idea,hope,believe,hope,thought,doubt.truth,order,suggestion, word etc.
(1) There is no doubt that he will come. There is doubt whether he will come.
Word came that Napoleon would come to inspect them. There is no possibility that….
(2) that引導的同位語從句與定語從句的區別：
在同位語從句中：that不可以省略，不作成分;定語從句的關係代詞that在定語從句作成分，作賓語時可以省略
We are interested in the news that some foreigners would visit our school.
We are interested in the news that he told us.
when, where引導的同位語從句與定語從句的區別：
在定語從句中，when, where前有分別表示時間、地點的先行詞；而在同位語從句中無此對應關係
They have no idea at all where he has gone.(同位語從句)
Go and get your coat. It’s in the place where you left it.(定語從句)
5. 疑問詞-ever既可以引導名詞性從句，也可以引導讓步狀語從句，而no matter+疑問詞只能引導讓步狀語從句
No matter where I go, my heart is towards China.
I believer whatever he says. Whatever he says, I will never believe him.
who與 whoever的區別
who是「誰」的意思，表示具有疑問，who相當於anyone who「無論誰」
Whoever leaves the room last ought to turn off the lights.
Can you tell me who that gentleman is?
6．當名詞性從句缺少主語、賓語或表語時，引導詞通常用what，它相當於。另外，有時具有感嘆意義all that, anything that或 the thing(s) that
What we can’t get seems better than what we have.
Tom thought what a beautiful girl Mary was.
7.注意區分it 作形式主語的主語從句與強調句
強調句句型It is/was+被強調部分+that, 去掉It is/was, that，句子仍然成立。
It is natural that they should have different views. 主語從句
It is only lately that he had had a family himself. 強調句
What was it that he wanted? I don’t know what it was that he wanted.
It was in the hotel where he stayed that we discussed the serious problem
8.注意it 作形式主語的主語從句和as引導非限制性定語從句引導的不同
It is known to all that the earth is round. As is known to all， the earth is round.
練習題：
1. I want to be liked and loved for ________ I am inside.
A. who B. where C. what D. how
2. -It’s no use having ideas only.
-Don’t worry .Peter can show you_________ to turn an idea into an act.
A. how B. who C. what D. where
3._________ some people regard as a drawback is seen as a plus by many others.
A. Whether B. What C. That D. How
4. Part of the reason Charles Dickens loved his own novel, David Copperfield, was _______it
was rather closely modeled on his own life.
A. what B. that C. why D. whether
5. -I prefer shutting myself in and listening to music all day on Sundays.
-That’s ________ I don’t agree. You should have a more active life.
A. where B. how C. when D. what
6. News came from the school office ____ Wang Lin had been admitted to Beijing University.
A. which B. what C. that D. where
7. Almost everyone has his own strengths and weaknesses. It is _______ others are weak that maybe you have a great advantage.
A. as B. where C. that D. what