1、一名词性从句在句子中起名词作用的各种从句统称为名词性从句。这类从句在句中可担任主语、表语、宾语和同位语，名词从句可以分为主语从句、表语从句、宾语从句和同位语从句。1.主语从句在句子中担当主语的是一个句子，这个从句就叫作主语从句。主语从句可以由下列连词、连接代词和连接副词引导，且不能省略。连词：that, whether连接代词：what, whatever, who, whoever 等连接副词：when, where, how, why(1)由连词 that, whether 引导的主语从句连词 that, whether 在从句中的作用只是引导主语从句，它在从句中不担任成分，不能省略，且由
2、 that, whether 引导的主语从句，多用 it 多形式主语e.g That the earth is round is true.=It is true that the earth is round.地球是圆的，是一个事实。Whether hell come or not hasnt been decided.= It hasnt been decided whether hell come or not.(2)由连接代词或连接副词引导的主语从句连接代词 who, which 和连接副词 when, where, how, why 都可以引导主语从句，它们分别在从句中担任主语、宾语
3、和状语，不能省略，翻译时，不能把它们译为疑问句，由它们引导的主语从句，也可以用形式主语 it 引导e.g Who let out the news remained unknown. =It remained unknown who let out the news. When well start is not clear. =It is not clear when well start.我们何时出发还不清楚。(3)以关系代词 what, whatever, whoever, whomever, whichever 引导的主语从句不能用形式主语 it 引导，它们在句子中担任成分，不能省略，
4、语序为陈述语序。e.g What he said at the meeting is important.他在会上所说的事情是重要的。Whoever leaves the office should tell me.无论是谁离开办公室都应该告诉我。(4)用 it 作形式主语的主语从句结构a. It is +名词+从句 It is a fact that 事实是类似的名词还有：a pity； no wonder；等。b. It is +形容词 +从句It is necessary that 有必要It is clear that 很清楚It is likely that 很可能It is imp
5、ortant that 重要的是It is essential that he should be here by the weekend .周末之前，他应该到这里是必要的。c. It is +过去分词+从句It is said that 据说 It is reported that 据报道d. It +不及物动词+ 从句It seems that 好像是 It happened that 碰巧It now appears that they are in urgent need of help. 2. 宾语从句用作宾语的从句叫宾语从句。1.引导宾语从句的关联词有三类：(1) 从属连词 tha
6、t。如：He told us that he felt ill. 他对我们说他感到不舒服。I know he has returned. 我知道他已经回来了。注： that 在引导宾语从句时也并不是任何情况下都可以省略。在以下情况下，that 不能省略。1. Everybody could see what happened and that Tom was frightened. and 连接两个宾语从句，that 宾语从句放在 and 的后面时，that 不能省略。2. I know nothing about him except that he is from the south. t
7、hat 引导的宾语从句作介词宾语时，that 不能省略。主句谓语动词与 that 从句之间有插入语，that 不可省略。(2)从属连词 if/whether。如：I doubt whether he will succeed. 我怀疑他是否会成功。I dont know if you can help me. 我不知道你能否帮助我。(3)连接代词 who, whom, whose, what, which, whoever, whatever, whichever连接副词 where, when, how, why。I wonder what hes writing to me about.
8、我不知道他要给我写信说什么事。Ill tell you why I asked you to come. 我会告诉你我为什么要你来。2. 介词宾语从句宾语从句也可用作介词的宾语。如：He was deeply displeased by what had occurred that day.他对那天发生的事感到很不快。注意：连词 that 引导的名词性从句很少作介词的宾语，只用在 except, but, in 后。3. 动词itthat 结构如果宾语从句后还有宾语补足语，则用 it 作形式宾语，而将宾语从句后置。如：We thought it strange that Xiao Wang d
9、id not come yesterday.He has made it clear that he will not give in.他已表明他不会屈服。4. 某些形容词或过去分词后常接宾语从句，这类形容词或过去分词有 sure, glad, certain, pleased, happy, afraid, surprised, satisfied 等，连词 that 可省略。如：I am not sure what I ought to do.我不能确定我该做什么。5. 连词 whether (or not)或 if 引导的宾语从句if 和 whether 引导的宾语从句可以互换使用，但
10、whether 常和 or not 连用，if 一般不与 or not 连用。如 I wonder whether it is true or not. 我不知它是真是假。3. 表语从句表语从句放在连系动词之后，充当复合句中的表语, 一般结构是“主语连系动词表语从句” 。可接表语从句的连系动词有 be，look，seem，sound，appear 等。The question remains whether they will be able to help us.问题还是他们能否帮我们。At that time，it seemed as if I couldnt think of the r
11、ight word. 引导表语从句的关联词的种类：(1）从属连词 thate.g The trouble is that I have lost his address. 麻烦是我把他的地址丢了。that 是连词 ,没有词义，在句中不作成分，因此一般不可省略(但在口语中有时 that 可省略)。(2) 从属连词 whether，as，as if / though 引导的表语从句。如：He looked just as he had looked ten years before.他看起来还与十年前一样。It sounds as if someone is knocking at the doo
12、r.听起来好像有人在敲门。(3) because，why 引导的表语从句。如：Thats because he didnt understand me.那是因为他没有理解我（Thats because强调原因）Thats why he got angry with me.那正是他对我生气的原因。 （Thats why强调结果）注意：表示结果或名词 reason 作主语时，后面的表语从句表示原因时要用 that 引导，不宜用 because.如：The reason why I was sad was that he didnt understand me.我难过的原因是他没有理解我。(4) 连
13、接代词 who，whom，whose，what，which，whoever，whatever，whichever连接副词 where，when ，how ，whye.g The problem is who we can get to replace her. 问题是我们能找到谁去替换她呢。The question is how he did it. 问题是他是如何做此事的。That was what she did this morning on reaching the attic. 那就是她今晨上了阁楼干的。(5) 使用虚拟语气的表语从句在表示建议、劝告、命令含义的名词后的表语从句，谓语
14、动词需用“should+动词原形” 表示，should 可省略。常见的词有： advice，suggestion，order，proposal，plan，idea 等。e.g My suggestion is that we （should ） start early tomorrow. 我的建议是我们明天一早就出发。4. 同位语从句英语中有一些名词如 fact, idea, news, word, hope, promise, suggestion, reply, problem, belief, doubt, truth, order, thought 等，它们本身有一定的意义，但表达得不
15、够具体。为了使其表达的意义更加具体明确，其后常跟有一个从句，用来补充说明该名词的内容，这个从句就叫做同位语从句。(1) 同位语从句的引导词表示陈述意义时通常用 that。注意 that 不能省略。同位语从句说明的名词常见的有：ability, advice, answer, belief, doubt, discovery, fact, fear, hope, idea, information, message, news, order, possibility, problem, proposal, question, story, suggestion, theory, thought,
16、 word(消息) 等,同位语从句一般都是用来解释说明一些抽象名词，而不可说明的名词是不会接同位语从句的。比如：man, water, sun 等具体的人或事物。e.g There is no doubt that the prices of cars will go down. The belief that the company will make a great is shared by everyone.表示“是否”的意思时只能用 whether，不能用 if。这一点与主语从句相似。e.g The question whether he can finish the work wit
17、hin two days remains unknown.表示疑问时也可用其他引导词 where, when, why, how, who, what 来引导。e.g This student asked a good question why pollution cant be stopped. I have no idea where I should go.I have no idea how I can get to the railway station.(2) 同位语从句和定语从句的区别 定语从句相当于一个形容词, 它对先行词起修饰、描述和限制的作用。同位语从句相当于名词，属于名词
18、性从句，它是对前面名词内容的具体表述，它们之间的关系是同位关系。试比较： The news that you heard is not true. 你听到的那个消息不是真的。 （定语从句） The news that he has died is true. 他已经去世的消息是真的。 （同位语从句，说明了 news 的具体内容，即 he has died） 同位语从句常跟在 news, fact, promise, idea, word, message, hope, truth, answer, proposal, suggestion, order, information 等少数名词之后
19、，而一般名词之后都可跟定语从句。e.g He didnt give the answer why he was late. 他没回答他为什么迟到这个问题。 （同位语从句） Then rose a question where we should go. 于是产生了一个问题：我们该到哪里去？（同位语从句） that 在定语从句中充当某一成分, 是关系代词; that 在同位语从句中不作任何成分，仅把主句与从句连接在一起，是从属连词。如： The fact that just now you talked about interests me. The fact that he failed in
20、 the exam made his parents very angry. 他考试没及格这个事实使他的父母很生气。 （同位语从句） when, where, why, how, who, whom, which 如果引导定语从句, 它们分别指前面先行词所表示的时间、地点、原因、方式、人和物，否则引导的就是同位语从句。试比较： I still remember the day when he was killed. 我还记得他被害的那一天。(定语从句) I have no idea when he was killed. 我不知道他什么时候被害的。 （同位语从句） They didnt go
21、to the town where they were born.他们没有去他们出生的小镇。 (定语从句) They didnt answer the question where they were born.他们没有回答他们在哪里出生这个问题。（同位语从句） whether, what 可引导同位语从句，但通常不可引导定语从句。 e.g We have no information whether he is alive. 我们不知道他是否活着。 （同位语从句） Next comes the question what step we should take. 接着的问题是我们下一步该做什
22、么。（同 位语从句）1. Exactly how the tomato was introduced into Europe is uncertain, but it was probably around 1565. 2. Grandma pointed to the hospital and said, “Thats when I was born.” 3. “Every time you eat a sweet, drink green tea.” This is that my mother used to tell me. 4. It makes the book so extrao
23、rdinary is the creative imagination of the writer. 5. From space, the earth looks blue. This is how about seventy-one percent of its surface is covered by water. 6. It suddenly occurred to him he had left his keys in the office. 7. As many as five courses are provided, and you are free to choose wha
24、tever suits you best.8. It doesnt matter if you pay by cash or credit card in this store. 9. Our teachers always tell us to believe in that what we do and who we are if we want to succeed.10. When the news came how the war broke out, he decided to serve in the army.1. He told me _ he would go to col
25、lege the next year.2. I dont know _ there will be a bus.3. I really dont know _ you should depend on if you dont depend on your parents.4. He didnt tell me _ he would come back from Shanghai next time.5. Let me know _ train youll be arriving on.6. Can you work out _ much we will spend during the tri
26、p?7. Make sure _ there are no mistakes in your papers before you turn them in.8. We all know _she is an intelligent girl.9. I was uncertain _he could pass the exam or not.10. What he did was quite different from_he said.11. I guess you will soon find out _sent you these beautiful flowers. 12. I dont
27、 know_book I should buy.13. The most exciting moment was _Tom kicked The final goal in the last minute. 14_ he has been admitted to a key university makes his parents happy.15_the Amber Room still exists in the world remains a mystery.16._ is known to all is that the 2008 Olympic Games will take pla
28、ce in Beijing. 17._surprised me most was that the boy can recite over 70 poems.18._ will take charge of the organizations is not important.19._ saved the girl is not clear.20. _ breaks the law should be punished.21. _book I should choose among these is hard for me.22_the dinosaurs disappeared remain
29、s a mystery.23_they solved the problem interested me.24 It hasnt been known to all _ the meeting will take place next October.25.The idea _ computers can recognize human voice surprises many people.26.We will discuss the problem_the sports meeting will be held on time.27.I have no idea _ he is.28 .Next comes the question _you want to put in the box.
