由一個(gè)主句和一個(gè)或一個(gè)以上的從句構(gòu)成的句子叫復(fù)合句。名詞性從句在復(fù)合句中起名詞的作用，它包括主語(yǔ)從句、賓語(yǔ)從句、表語(yǔ)從句、同位語(yǔ)從句四大類(lèi)，在句中分別用作主語(yǔ)、賓語(yǔ)、表語(yǔ)和同位語(yǔ)。
引導(dǎo)名詞性從句的關(guān)聯(lián)詞
A.that
連詞that本身沒(méi)有意義，在從句中不擔(dān)任任何句子成分，在賓語(yǔ)從句中有時(shí)可省略。
I hear (that) he has joined the football club. 我聽(tīng)說(shuō)他已經(jīng)加入了足球俱樂(lè)部。
That light travels in straight line is known to all. 眾所周知，光是以直線傳播的。
It so happens that I know the man. 碰巧我認(rèn)識(shí)那個(gè)。
Is it certain that they will win 他們一定會(huì)贏嗎
B.whether和if
連詞whether和if本身有意義(解釋是否)，在從句中不可省略。
1.whether可以連接所有的名詞性從句，而if只能引導(dǎo)賓語(yǔ)從句。
I didn't know whether he would attend the concert. 我并不知道他是否參加音樂(lè)會(huì)。(賓語(yǔ)從句，可用if代替whether)
The question is whether it s worth trying. 問(wèn)題是值不值得試一試。(表語(yǔ)從句，不可用if代替whether)
Whether she comes or not makes no difference. 她來(lái)不來(lái)都沒(méi)有關(guān)系。(主語(yǔ)從句，不可用if代替whether)
He must answer the question whether he agrees to it or not. 他必須回答他是否同意此事這樣一個(gè)問(wèn)題。(同位語(yǔ)從句，不可用if代替whether)
2.whether引導(dǎo)的賓語(yǔ)從句可作介的賓語(yǔ)，而if則不能。
It all depends on whether they will support us. 這完全取決于他們是否支持我們。(不用if)
Ryan was worrying about whether he had hurt her feelings. 瑞恩擔(dān)心是否傷害了她的感情。
3.if既可引導(dǎo)語(yǔ)從句，也可引導(dǎo)賓語(yǔ)從句。如果用if會(huì)引起歧義，應(yīng)避免使用if，而用whether。
Please let me know if you want to join us. 請(qǐng)告訴我你是否想加入我們。(if引導(dǎo)的從句可被看成是賓語(yǔ)從句，if表示是否)
Please let me know if you want to join us. 如果你想加入我們的話，請(qǐng)告訴我一聲。(if引導(dǎo)的從句可被看成是條件狀語(yǔ)從句，if表示如果)
Please let me know whether you want t join us. 請(qǐng)告訴我你是否想加入我們。(為避免引起歧義，可用whether表示是否)
C.who, whom, whose, what, which
連接代詞who, whom, whose, what, which等在從句中既起連接作用，同時(shí)又擔(dān)當(dāng)主語(yǔ)、賓語(yǔ)、定語(yǔ)、表語(yǔ)等成分。
No one knows who he was waiting for. 沒(méi)人知道他當(dāng)時(shí)在等誰(shuí)。
We are worrying about what we should do next. 我們正在為下一步該怎么辦而煩惱。
Tell me whos house it is. 告訴我這是誰(shuí)的家。
Let me know which train you will be arriving on. 告訴我你將乘哪列火車(chē)到達(dá)。
D.where, when, how, why
連接副詞where, when, how, why等在從句中既是連接詞，又作狀語(yǔ)。
I don't know where we are going to have the meeting.我不知道我們將在哪兒開(kāi)會(huì)。
She always thinks of how shecan work well. 她總是在想怎樣能把工作做好。
What I am anxious to know is when we can visit the museum. 我急于知道我們什么時(shí)候能參觀博物館。
比較：
when引導(dǎo)的時(shí)間狀語(yǔ)從句和名詞性從句中的不同時(shí)態(tài)。
Please lt me know when you arrive. 你到的時(shí)候，請(qǐng)告訴我一聲。(when引導(dǎo)的是時(shí)間狀語(yǔ)從句，從句中用一般現(xiàn)在時(shí)來(lái)表示將來(lái)。)
Please let me know when you will arrive. 請(qǐng)告訴我你什么時(shí)候到。(when引導(dǎo)的是賓語(yǔ)從句，從句中用一般將來(lái)時(shí)。)
E.whoever, whomever, whatever, whichever, whosever
連接代詞whoever = anyone who任何人, 無(wú)論誰(shuí);whatever =anything that凡是...，無(wú)論什么;whichever = anything that無(wú)論那一個(gè), 任何一個(gè);whomever = anyone whom (whoever的賓格形式)。
Whoever comes to the club is welcome. 不論誰(shuí)來(lái)參加這個(gè)俱樂(lè)部都?xì)g迎。
Whatever is worth doing at all is worth doing well.凡是值得做的就值得做好。
They ate whatever they could find o the deserted island. 他們?cè)诨膷u找到什么就吃什么。
You may do whatever you will. 你可做任何你想做的事。
I'll take whichever book interests me.我愿買(mǎi)任何讓我感興趣的書(shū)。
Whosever book is overdue will be fined. 不管誰(shuí)的書(shū)過(guò)期未還都要被罰款。
比較：
連接代詞whoever在賓語(yǔ)從句中作主語(yǔ)，whomever作賓語(yǔ)從句中賓語(yǔ)。
You may offer he book to whoever wants it. 你可把這本書(shū)給任何想要的人。(此句中不能使用whomever，因?yàn)閣hoever在賓語(yǔ)從句中作wants it的主語(yǔ))
You may offer the book to whomever you like.你可把這本書(shū)給任何你喜歡的人。(whomever在賓語(yǔ)從句中作you like的賓語(yǔ))
表語(yǔ)從句
表語(yǔ)從句放在連系動(dòng)詞之后，充當(dāng)復(fù)合句中的表語(yǔ)。
A.可接表語(yǔ)從句的連系動(dòng)詞
可接表語(yǔ)從句的連系動(dòng)詞有be, look, seem, sound, appear等。
China is no longer what she used to be. 今日的中國(guó)不再是過(guò)去的中國(guó)了。
The question remains whether they will be able to help us. 問(wèn)題還是他們能否幫我們。
Itappears that he has a taste for music.看來(lái)他對(duì)音樂(lè)有一定的鑒賞力.
At that time, it seemed as if I couldn' t think of the right word anyhow. 當(dāng)時(shí)，我似乎怎么也想不出一個(gè)恰當(dāng)?shù)淖盅蹃?lái)。
B.as, as ifthough引導(dǎo)的表語(yǔ)從句
He looked just as he had looked ten years before. 他看起來(lái)還與十年前一樣。
It sounds as ifsomeone is knocking at the door. 聽(tīng)起來(lái)好像有人在敲門(mén)。
C.because, why引導(dǎo)的表語(yǔ)從句
I think it is because you are talking too much. 我想這是因?yàn)槟阍捳f(shuō)得太多。
That's because he didn't understand me. 那是因?yàn)樗麤](méi)有理解我。(That's because
同位語(yǔ)從句
同位語(yǔ)從句用于對(duì)前面的名詞作進(jìn)一步解釋?zhuān)f(shuō)明名詞的具體內(nèi)容。同位語(yǔ)從句一般由that引導(dǎo)，但也可以由whether 以及連接代詞和連接副詞引導(dǎo)。
A.同位語(yǔ)從句一般跟在名詞fact, hope, idea, news, doubt, suggestion, information, opinion, decision, discovery, truth, promise, statement, problem, rule等的面。
They were all very much worried over the fact that you were sick. 對(duì)你生病這件事，他們都很焦慮。
Where did you get the idea that I could not come 你在哪兒聽(tīng)說(shuō)我不能來(lái)?
I have no idea whether he'll come or not. 我不知道他是否來(lái)。
We haven't yet settled the question where we are going t spend our summer vacation. 到哪兒去度暑假，這個(gè)問(wèn)題我們還沒(méi)有決定。
It is a question how he did it. 那是一個(gè)他如何做了此事的問(wèn)題。
There is no doubt that we will win. 毫無(wú)疑問(wèn)我們會(huì)贏的。
注意：
當(dāng)含有同位語(yǔ)從句的主句謂語(yǔ)部分過(guò)短時(shí)，可以把謂語(yǔ)動(dòng)詞提前，使同位語(yǔ)從句與名詞隔開(kāi)，以避免頭重腳輕的現(xiàn)象。
Word came that Mr President would come and inspect ourschool himself. 有消息說(shuō)總統(tǒng)先生將親自來(lái)視察我們學(xué)校。
B.使用虛擬語(yǔ)氣的同位語(yǔ)從句
在一些表示建議、命令、要求的名詞后的同位語(yǔ)從句中，謂語(yǔ)動(dòng)詞用should+動(dòng)詞原形表示，should可省略。
This is our only request that this (hould) be settled as soon as possible. 盡快解決這個(gè)問(wèn)題，這是我們唯一的請(qǐng)求。
He made the suggestion that we go by train. 他建議我們坐火車(chē)去。
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