【语法】名词性从句（一）

Ⅰ.名词性从句的结构和功能：名词性从句包括主语从句、宾语从句、表语从句、同位语从句。名词性从句主要有四种从句结构：以that引导的从句；以whether/ if引导的从句，以特殊疑问词引导的从句；以what或wh-ever等连接代词引导的名词性关系从句。此外，as if/ as though也可引导表语从句。 Ⅱ.名词性从句的连接词：引导名词性从句的连接词有：从属连词、连接代词和连接副词。

1. 从属连词：that(本身无意义)，whether(是否)，if(是否)。只起连接作用，在从句中不作任何成分。
2. 连接代词：who, whom, whose, which, what, whatever, whoever等。它们除起连接作用外，还可在从句中充当主语、宾语、定语、表语等成分。
3. 连接副词：when(＝the time when什么时候，何时)，where(＝the place where什么地方，何地)，how(＝the way that/in which怎样，以……方式，如何)，why＝the reason why为什么)。它们除起连接作用，还在从句中作状语。温馨提示：what与that引导名词性从句的区别：
4. what在名词性从句中可充当主语、宾语和表语，意义上相当于the thing(s) that，引导主语从句时，其谓语动词的单复数依句意而定。e.g. What the lecturer said is very valuable.We wonder what he will do next.
5. that引导名词性从句不充当任何句子成分，只起连接作用，无任何意义。引导主语从句时，常用it作形式主语，谓语动词用单数，引导宾语从句时，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.名词性从句的分类以及用法：（一）主语从句：
6. 主语从句的基本用法：

1. that引导的主语从句既可放在句首，也可放在句尾，that起连接作用，无词义，在从句中不作成分，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.
2. whether引导的主语从句可放在句首，也可放在句尾；if引导的主语从句只能放在句尾，前面需要it作形式主语。whether/ if 起连接作用，“是否”，在从句中不作成分。e.g. Whether he will go there or not is not clear.It is doubtful whether/ if the work can be completed.
3. wh-类连接词引导的主语从句：wh-类连接词包括wh-类的连接代词(who, whom, whose, which, what, whoever, whomever, whichever, whatever等)和连接副词(when, where, how, why, whenever, wherever, however等)。what, when和wh-ever类的词有时可不表疑问。wh-类连接代词在句中既起连接作用，又可充当主语、宾语、表语、定语等成分。wh-类连接副词在句中起连接作用，在从句中可充当时间、地点、原因、方式状语。

1. 主语从句的单复数问题

1. 从句作主语时，谓语动词一般用单数。e.g. That he will come and help us is certain.Who will go to the energy conference is not important.
2. what引导的从句作主语，表示单数概念，谓语动词一般用单数形式；表示复数概念，则谓语动词常用复数。e.g. What he said is true.What he needs are books.

（二） 宾语从句：

1. 宾语从句的基本用法：

1. 动词后接宾语从句的用法：e.g. I know that he is friendly and hospitable.Go to stamp sales and buy whatever you can afford.温馨提示1：doubt, doubtful与sure后名词性从句连接词that, whether, if的选择。①当doubt, doubtful用于肯定句时，后面的名词性从句的连接词常用whether或if；当doubt, doubtful用于否定句或疑问句时，后面名词性从句的连接词用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当be sure用于肯定句时，后面的宾语从句的连接词常用that；当be sure用于否定句时，后面的宾语从句的连接词常用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.
2. 介词及形容词后接宾语从句的用法：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.温馨提示2：①一般情况下介词后只能用wh-类连接词引导的宾语从句。e.g. I am surprised at what he said.②介词后如果接that从句，要先加上it，再加that从句，即“介词＋it＋that…”结构。e.g. You may depend on it that they will support you.③介词except, but, besides及in后可接that从句。e.g. I know nothing about him except that he lives here.④常接宾语从句的形容词有sure, certain, glad, pleased, happy, afraid, surprised, satisfied, sorry等。e.g. I’m afraid he won’t attend our wedding.
3. that引导的宾语从句：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.温馨提示3：在suggest, demand, order, insist等动词之后的宾语从句中用虚拟语气，“(should＋)动词原形”。e.g. He suggested that we (should) set about doing the work at once.
4. whether/ if 引导的宾语从句：e.g. I’ll try to find out whether/ if the machine is in good condition.温馨提示4：① whether/ if引导宾语从句表示“是否”的意思时，一般情况下可互换。② if引导宾语从句时可以有否定式，而whether从句则没有。e.g. I don’t care if he doesn’t come.
5. 特殊疑问词引导的宾语从句：由who, what, how, which, whose, where, why等词引导的宾语从句，可作动词、介词及形容词的宾语。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.温馨提示5：如果疑问词是介词的宾语，介词可位于从句句首或句末。e.g. I didn’t know in which building they lived.＝I didn’t know which building they lived in.

1. 宾语从句的时态:

1. 主句为现在或将来时态主句谓语动词如果是现在时或将来时，从句谓语动词可用任何所需要的时态。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.
2. 主句为过去时态主句的谓语动词是一般过去时，从句的谓语动词要用相应的过去时态。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.
3. 表示客观事实或真理如果从句表示客观事实或真理，不管主句的谓语动词是何时态，从句都要用现在时态。e.g. The teacher said that the world is made up of matter.

（三） 表语从句:

1. 表语从句的基本用法:

1. 基本结构：主语＋系动词＋表语从句，常用的系动词有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.
2. as if/ as though引导的表语从句，系动词通常为look，seem，sound等，从句可以用陈述语气，也可以用虚拟语气。e.g. It looks as if it is/ were going to snow.
3. that和what引导的表语从句的区别：that引导表语从句时，起连接作用，没有实际意义，不作句子成分；what引导表语从句时，既充当连接代词，又作句子成分。e.g. Our plan is that we’ll go there once a week.That’s what he said.
4. 由连接副词引导的表语从句：连接副词where，why，when等引导表语从句，分别在从句中作地点、原因、时间状语。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．表语从句需要注意的问题
5. 主语为名词reason，表语从句用that而不用why引导。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.
6. 引导表语从句时，用whether，不能用if。e.g. The question is whether he has signed the contract. (不能用if)
7. 表语从句中的虚拟语气：如果主句的主语是名词idea, advice, suggestion, order, request, requirement等时，则表语从句的谓语应用虚拟语气，“(should＋)动词原形”。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.
8. 使用连接词时的注意事项：连接代词和连接副词一般都表疑问，但what, when和where等连接词有两种含义，一种表示疑问，一种表示陈述。表陈述时，相当于the thing that, the time when, the place where, 常意为“……的人/事”、“……的时间”、“……的地点”等。e.g. This is where he once lived.This is what I want to know.That was when he did the experiment.

1. 比较三个句式:
   

（四）同位语从句:在主从复合句中作同位语的从句，叫同位语从句。表示名词的内容，加以解释。同位语从句的基本用法：

1. 能接同位语从句的名词：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。
2. that引导的同位语从句：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.温馨提示:同位语从句通常由that引导，但根据接同位语的名词不同，也可由whether, when, who, how, what, why等引导。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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