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从句一般有三类。1. 名词性从句： 主语从句 表语从句 宾语从句 同位语从句2. 定语从句3. 状语从句：时间状语从句，地点状语从句，原因状语从句，结果状语从句，条件状语从句，目的状语从句，让步状语从句，方式状语从句，比较状语从句从句的学习重点就是在于它们的连接词（在定语从句中成为关系词，在状语从句中成为从属连词）。比如名词性从句，连接词可以分为三类：连词：that，whether，if，as if等；连接代词：which，what，who，whose，whom等；连接副词：when, why, where, how等；想想为什么会有这三种分类，肯定是有它们的区别的，比如是连词引导的名词性从句，后面应当是完整的句子，如，i know that he is from America. 主 谓 宾（其中that为连接词，he is from America是一个完整的句子）如果是连接代词的话，表示代得是句子中的某个成分，如， i don't know what his name is. 主 谓 宾（其中what是连接词，在从句中充当is 的表语）把连接词弄清楚了，从句就很清晰了。
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一．主语从句 主语从句是在复合句中充当主语的从句,通常放在主句谓语动词之前或由形式主语it代替,而本身放在句子末尾. 1. It 作形式主语和it引导强调句的比较 It 作形式主语代替主语从句,主要是为了平衡句子结构,主语从句的连接词没有变化.而it引导的强调句则是对句子某一部分进行强调,无论强调的是什么成分,都可用连词that.被强调部分指人是也可用who/whom.例如： It is a pity that you didn’t go to see the film. It doesn’t interest me whether you succeed or not. It is in the morning that the murder took place. It is John that broke the window. 2. 用it 作形式主语的结构 (1) It is ＋名词＋从句 It is a fact that … 事实是… It is an honor that …非常荣幸 It is common knowledge that …是常识 (2) it is ＋形容词＋从句 It is natural that… 很自然… It is strange that… 奇怪的是… (3) it is ＋不及物动词＋从句 It seems that… 似乎… It happened that… 碰巧… (4) it ＋过去分词＋从句 It is reported that… 据报道… It has been proved that… 已证实… 3. 主语从句不可位于句首的五种情况 (1) if 引导的主语从句不可居于复合句句首. (2) It is said , (reported) …结构中的主语从句不可提前.例如： It is said that President Jingo will visit our school next week. (right) That President Jiang will visit our school next week is said. (wrong) (3) It happens…, It occurs… 结构中的主语从句不可提前.例如： It occurred to him that he failed in the examination. (right) That he failed in the examination occurred to him. (wrong) (4) It doesn’t matter how/whether …结构中的主语从句不可提前.例如： It doesn’t matter whether he is wrong or not. (right) Whether he is wrong or not doesn’t matter. (wrong) (5) 含主语从句的复合句是疑问句时,主语从句不可提前.例如： Is it likely that it will rain in the evening? (right) Is that will rain in the evening likely? (wrong) 4. What 与that 在引导主语从句时的区别 What 引导主语从句时在句时在从句中充当句子成分,如主语．宾语．表语,而that 则不然.例如： 1) What you said yesterday is right. 2) That she is still alive is a consolation. 二．宾语从句 宾语从句就是在复合句中作宾语的名词性从句,通常放在主句谓语动词（及物动词）或介词之后. 1. 作动词的宾语 (1) 由that引导的宾语从句（that 通常可以省略）,例如： I heard that be joined the army. (2) 由what, whether (if) 引导的宾语从句,例如： 1) She did not know what had happened. 2) I wonder whether you can change this note for me. (3) 动词＋间接宾语＋宾语从句.例如： She told me that she would accept my invitation. 2. 作介词的宾语 例如：Our success depends upon how well we can cooperate with one another. 3. 作形容词的宾语 例如：I am afraid (that) I’ve made a mistake. That 引导的从句常跟在下列形容词后作宾语： Anxious, aware, certain, confident, convinced, determined, glad, proud, surprised, worried, sorry, thankful, ashamed, disappointed, annoyed, pleased, hurt, satisfied, content 等.也可以将此类词后的that 从句的看作原因状语从句. 4. It 可以作为形式宾语 It 不仅可以作为形式主语,还可以作为形式宾语而真正的宾语that 从句则放在句尾,特别是在带复合宾语的句子中. 例如： We heard it that she would get married next month.. 5. 后边不能直接跟that 从句的动词 这类动词有Allow, refuse, let, like, cause, force, admire, condemn, celebrate, dislike, love, help, take, forgive等.这类词后可以用不定式或动名词作宾语,但不可以用that引导的宾语从句.例如： I admire their winning the match. (right) I admire that they won the match. (wrong) 6. 不可用that从句作直接宾语的动词 有些动词不可用于“动词＋间接宾语＋that从句“结构中,常见的有Envy, order, accuse, refuse, impress, forgive, blame, denounce, advise, congratulate等.例如： He impressed the manager as an honest man. (right) He impressed the manager that he was an honest man. (wrong) 7. 否定的转移 若主句谓语动词为Think, consider, wuppose, believe, expect, fancy, guess, imagine等,其后的宾语从句若含有否定意义,一般要把否定词转移到主句谓语上,从句谓语用肯定式.例如： I don’t think this dress fits you well.（我认为这件衣服不适合你穿.） 三．表语从句 表语从句在复合句中作表语的名词性从句,放在系动词之后,一般结构是“主语＋连系动词＋表语从句”.可以接表语从句的连系动词有be, look, remain, seem等.引导表语从句的that常可省略.另外,常用的还有the reason is that… 和It is because 等结构.例如： 1) The question is whether we can make good preparation in such a short time. 2) This is why we can’t get the support of the people 3) But the fact remains that we are behind the other classes. 4) The reason he is late for school is that he missed the early bus. 四．同位语从句 同位语从句就是在复合句中作名词的同位语的名词性从句. 1. 同位语从句的功能 同位语从句对于名词进一步解释,说明名词的具体内容,一般由that引导,例如： 1) The king’s decision that the prisoner would be set free surprised all the people. 2) The order that all the soldiers should stay still is given by the general. 2. 同位语在句子中的位置 同位语从句有时可以不紧跟在它所说明的名词后面,而是被别的词隔开.例如： He got the news from Mary that the sports meeting was put off. 3. 同位语从句与定语从句的区别 (1) 定语从句中的that既代替先行词,同时以在从句中作某个成分（主语或宾语）,而同位语从句中的that是连词,只起连接主句与从句的作用,不充当句中任何成分. (2) 定语从句是形容词性的,其功能是修饰先行词,对先行词加以限定,描述定的性质或特征；同位语从句是名词性的,其功能是对名词进行补充说明.例如： 1) The news that he told me is that Tom would go abroad next year.（他告诉我的消息是汤姆明年将出国.）（第一个that引导的从句是定语从句,that在从句中作宾语） 2)The news that Tom would go abroad is told by him.（汤姆将出国的消息是他讲的.）（同位语从句,that在句中不作任何成分）
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根据从句语法功能的不同可分为：主语从句、表语从句、宾语从句、同位语从句、定语从句和状语从句6类。
1、主语从句
主语从句就是作主语的从句。它的连接词有连词、连接副词、连词代词。主语从句放在句首时，句子显得很笨重，因此常用it作形式主语，而将真正的主语后置，比如：
It is a pity that you have missed such a wonderful concert.
真遗憾你错过了这么精彩的一场音乐会。
2、表语从句
表语从句就是作表语的从句。它的连接词有连词、连接副词、连词代词等。
比如：
My idea is that we meet at the bus stop.
我的想法是我们在公共汽车站会面。
3、宾语从句
宾语从句就是作宾语的从句。它的连接词有连词、连接副词、连词代词等。
比如：
She said that she would drop maths.
她说她要放弃数学。
4、同位语从句
同位语从句就是作同位语的从句，它的连接词有连词、连接副词等。
The fact that everyone loves beauty is common sense.
人人爱美是常识。
5、定语从句
定语从句就是作定语的从句。定语从句主要修饰、限定、描绘名词，有时修饰代词，放所修饰词后边。
比如：
The girl who wears a new dress is my daughter.
那个穿新衣服的女孩是我的女儿。
6、状语从句
状语从句就是作状语的从句。在复合句中修饰主句中的谓语动词、形容词或副词，起状语作用的从句叫作状语从句。
比如：
Soon after he jumps his parachute will open.
他跳伞之后，降落伞就会打开。
嘻哈寶萊
英语八大从句类型与用法总结举例如下：
一、定语从句：
在复合句中， 修饰名词或代词的从句叫定语从句，被修饰的名词或代词叫先行词，引导定语从句的有关系代词who，whom，whose，which，that等和关系副词where，when，why等，关系代词和关系副词在定语从句中担任句子成分。
二、状语从句：
表示“当…时候”的while，when，as的用法区别是：while从句中的谓语动词必须是延续性动词；表示带有规律性的“每当”或当主、从句谓语动词的动作发生有先后时，只能用when；当表示“一边…一边…”或“随着”时，只能用as，另外，用于此义的as所引导的时间状语从句谓语只能是动作动词，不能是状态动词。
三、名词性从句：
在句子中起名词作用的句子叫名词从句(NounClauses），名词从句的功能相当于名词词组,它在复合句中能担任主语、宾语、表语、同位语、介词宾语等，因此根据它在句中不同的语法功能，名词从句又可分别称为主语从句、宾语从句、表语从句和同位语从句。
英语从句
主语从句，宾语从句，表语从句和同位语从句。这4种属于名词性从句，相当于一个名词功效。
定语从句，相当于形容词功效。
状语从句，相当于副词功效。
