Ⅰ.名詞性從句的結(jié)構(gòu)和功能：名詞性從句包括主語從句、賓語從句、表語從句、同位語從句。名詞性從句主要有四種從句結(jié)構(gòu)：以that引導的從句；以whether/ if引導的從句，以特殊疑問詞引導的從句；以what或wh-ever等連接代詞引導的名詞性關(guān)系從句。此外，as if/ as though也可引導表語從句。 Ⅱ.名詞性從句的連接詞：引導名詞性從句的連接詞有：從屬連詞、連接代詞和連接副詞。
- 從屬連詞：that(本身無意義)，whether(是否)，if(是否)。只起連接作用，在從句中不作任何成分。
- 連接代詞：who, whom, whose, which, what, whatever, whoever等。它們除起連接作用外，還可在從句中充當主語、賓語、定語、表語等成分。
- 連接副詞：when(＝the time when什么時候，何時)，where(＝the place where什么地方，何地)，how(＝the way that/in which怎樣，以……方式，如何)，why＝the reason why為什么)。它們除起連接作用，還在從句中作狀語。溫馨提示：what與that引導名詞性從句的區(qū)別：
- what在名詞性從句中可充當主語、賓語和表語，意義上相當于the thing(s) that，引導主語從句時，其謂語動詞的單復數(shù)依句意而定。e.g. What the lecturer said is very valuable.We wonder what he will do next.
- that引導名詞性從句不充當任何句子成分，只起連接作用，無任何意義。引導主語從句時，常用it作形式主語，謂語動詞用單數(shù)，引導賓語從句時，常被省略。e.g. That she will refuse the offer seems unlikely.I have found (that) all the tickets have been sold out.It is a pity that you missed such a fine talk. Ⅲ.名詞性從句的分類以及用法：（一）主語從句：
- 主語從句的基本用法：
- that引導的主語從句既可放在句首，也可放在句尾，that起連接作用，無詞義，在從句中不作成分，一般不能省略。e.g. That we are invited to a concert this evening is good news to us.＝It is good news to us that we are invited to a concert this evening.
- whether引導的主語從句可放在句首，也可放在句尾；if引導的主語從句只能放在句尾，前面需要it作形式主語。whether/ if 起連接作用，“是否”，在從句中不作成分。e.g. Whether he will go there or not is not clear.It is doubtful whether/ if the work can be completed.
- wh-類連接詞引導的主語從句：wh-類連接詞包括wh-類的連接代詞(who, whom, whose, which, what, whoever, whomever, whichever, whatever等)和連接副詞(when, where, how, why, whenever, wherever, however等)。what, when和wh-ever類的詞有時可不表疑問。wh-類連接代詞在句中既起連接作用，又可充當主語、賓語、表語、定語等成分。wh-類連接副詞在句中起連接作用，在從句中可充當時間、地點、原因、方式狀語。
- 主語從句的單復數(shù)問題
- 從句作主語時，謂語動詞一般用單數(shù)。e.g. That he will come and help us is certain.Who will go to the energy conference is not important.
- what引導的從句作主語，表示單數(shù)概念，謂語動詞一般用單數(shù)形式；表示復數(shù)概念，則謂語動詞常用復數(shù)。e.g. What he said is true.What he needs are books.
（二） 賓語從句：
- 賓語從句的基本用法：
- 動詞后接賓語從句的用法：e.g. I know that he is friendly and hospitable.Go to stamp sales and buy whatever you can afford.溫馨提示1：doubt, doubtful與sure后名詞性從句連接詞that, whether, if的選擇。①當doubt, doubtful用于肯定句時，后面的名詞性從句的連接詞常用whether或if；當doubt, doubtful用于否定句或疑問句時，后面名詞性從句的連接詞用that。e.g. I doubt whether/ if he is at home.We don’t doubt that they can complete the task ahead of time.It is doubtful whether it is true or not.②當be sure用于肯定句時，后面的賓語從句的連接詞常用that；當be sure用于否定句時，后面的賓語從句的連接詞常用whether或if。e.g. We are sure that he is innocent.The old man didn’t seem to be sure whether/ if he had met me.
- 介詞及形容詞后接賓語從句的用法：e.g. We are talking about whether we admit students into our club.He was interested in whatever he saw there.He is pleased that he has passed a tough test.溫馨提示2：①一般情況下介詞后只能用wh-類連接詞引導的賓語從句。e.g. I am surprised at what he said.②介詞后如果接that從句，要先加上it，再加that從句，即“介詞＋it＋that…”結(jié)構(gòu)。e.g. You may depend on it that they will support you.③介詞except, but, besides及in后可接that從句。e.g. I know nothing about him except that he lives here.④常接賓語從句的形容詞有sure, certain, glad, pleased, happy, afraid, surprised, satisfied, sorry等。e.g. I’m afraid he won’t attend our wedding.
- that引導的賓語從句：e.g. We are glad that so many old friends will attend our tea party.The headmaster said that the school reports had been sent off.溫馨提示3：在suggest, demand, order, insist等動詞之后的賓語從句中用虛擬語氣，“(should＋)動詞原形”。e.g. He suggested that we (should) set about doing the work at once.
- whether/ if 引導的賓語從句：e.g. I’ll try to find out whether/ if the machine is in good condition.溫馨提示4：① whether/ if引導賓語從句表示“是否”的意思時，一般情況下可互換。② if引導賓語從句時可以有否定式，而whether從句則沒有。e.g. I don’t care if he doesn’t come.
- 特殊疑問詞引導的賓語從句：由who, what, how, which, whose, where, why等詞引導的賓語從句，可作動詞、介詞及形容詞的賓語。e.g. I can’t imagine how he did it.We are worrying about what we should do next.I wasn’t certain whose house I was in.溫馨提示5：如果疑問詞是介詞的賓語，介詞可位于從句句首或句末。e.g. I didn’t know in which building they lived.＝I didn’t know which building they lived in.
- 賓語從句的時態(tài):
- 主句為現(xiàn)在或?qū)頃r態(tài)主句謂語動詞如果是現(xiàn)在時或?qū)頃r，從句謂語動詞可用任何所需要的時態(tài)。e.g. She says that she works from Monday to Friday.I know he didn’t tell you that he would come then.He will tell me what happened to him during my absence.
- 主句為過去時態(tài)主句的謂語動詞是一般過去時，從句的謂語動詞要用相應的過去時態(tài)。e.g. He said there were no classes yesterday afternoon.He asked me if I was reading the book Red and Black when he came in.
- 表示客觀事實或真理如果從句表示客觀事實或真理，不管主句的謂語動詞是何時態(tài)，從句都要用現(xiàn)在時態(tài)。e.g. The teacher said that the world is made up of matter.
（三） 表語從句:
- 表語從句的基本用法:
- 基本結(jié)構(gòu)：主語＋系動詞＋表語從句，常用的系動詞有be，seem，remain，look等。e.g. My idea is that you should make good use of your time.It seems that he has been to America.
- as if/ as though引導的表語從句，系動詞通常為look，seem，sound等，從句可以用陳述語氣，也可以用虛擬語氣。e.g. It looks as if it is/ were going to snow.
- that和what引導的表語從句的區(qū)別：that引導表語從句時，起連接作用，沒有實際意義，不作句子成分；what引導表語從句時，既充當連接代詞，又作句子成分。e.g. Our plan is that we’ll go there once a week.That’s what he said.
- 由連接副詞引導的表語從句：連接副詞where，why，when等引導表語從句，分別在從句中作地點、原因、時間狀語。e.g. That is where the great writer used to live.That is why he didn’t pass the exam.That was when I was thirty.2．表語從句需要注意的問題
- 主語為名詞reason，表語從句用that而不用why引導。e.g. The reason why he was absent from the meeting was that he fell ill suddenly.The reason for such a serious accident is that the driver was too careless and drunk.
- 引導表語從句時，用whether，不能用if。e.g. The question is whether he has signed the contract. (不能用if)
- 表語從句中的虛擬語氣：如果主句的主語是名詞idea, advice, suggestion, order, request, requirement等時，則表語從句的謂語應用虛擬語氣，“(should＋)動詞原形”。e.g. My suggestion is that we (should) set out at once.The doctor’s advice is that you (should)rest more and drink more.
- 使用連接詞時的注意事項：連接代詞和連接副詞一般都表疑問，但what, when和where等連接詞有兩種含義，一種表示疑問，一種表示陳述。表陳述時，相當于the thing that, the time when, the place where, 常意為“……的人/事”、“……的時間”、“……的地點”等。e.g. This is where he once lived.This is what I want to know.That was when he did the experiment.
- 比較三個句式:
（四）同位語從句:在主從復合句中作同位語的從句，叫同位語從句。表示名詞的內(nèi)容，加以解釋。同位語從句的基本用法：
- 能接同位語從句的名詞：fact, idea, news, promise, information, message, belief, doubt, hope, opinion, possibility, thought, wish, truth, question, problem, reply, answer, report, suggestion, advice, order, warning等等。
- that引導的同位語從句：e.g. We were very excited at the news that our Chinese athletes won many gold medals.The problem that they can’t get here early is hard to solve.溫馨提示:同位語從句通常由that引導，但根據(jù)接同位語的名詞不同，也可由whether, when, who, how, what, why等引導。e.g. I have no idea when he will be back.The question who was to blame has never been settled.
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