求初中英语各类从句的用法

英语的复合句包括并列句和主从句两种.其中并列句是两句地位完全相同的简单句用表示并列关系的连词连接而成（例如and,or等）.主从句虽然有两套主谓结构,但是其中一套是主要的,称为主句,另一套只是充当主句的某个成分,称为从句.英语从句分为宾语从句,定语从句,状语从句,主语从句,表语从句,同位语从句6种.
宾语从句和表语从句
宾语从句和表语从句是从句中较为简单的一种.这两种从句是以句子的形式代替了主句中的宾语或表语,也就是直接占据了谓语后宾语或表语的位置,比较明显.引导宾语从句或表语从句的引导词最常用的是that,以及关系代词what,which,who(whom),关系副词when,where,how,whether.
由于主从复合句中有两套主谓结构,因而要注意时态的搭配.时态搭配的原则是从句服从主句,但是可以根据情况灵活配置,不过主从句之间不出现时段断层.因而一般常见的配置组合为：
主句 现在时 过去时 将来时
从句 现在时,过去时,将来时 过去的时态 一般现在时
注：当从句的内容是客观真理时,无论主句是什么时态,从句永远用一般现在时,例：The teacher told the students that the light travels faster than the sound in the air.
定语从句
定语从句是从句充当定语的用法,引导词与时态搭配的规则与宾语从句相同.定语从句与宾语从句区分的要点是宾语从句充当主句的宾语,占据了主句中宾语的位置,而定语从句的主句结构完整,定语从句在引导词的引导下跟在被修饰的主句的主语或宾语（表语）之后,起修饰作用,而被修饰的词语称为先行词.例如：
①People don’t know who runs in the morning in the park everyday.人们不知道是谁每天早晨在公园里跑步.
②People don’t know the man who runs in the morning in the park everyday.人们不知道那个每天早晨在公园里跑步的人是谁.
在②中,主句部分People don’t know the man句子结构是完整的,the man是被从句修饰的成分,即先行词.
注意,that是引导短语从句的引导词中最灵活而且用法最多的,通常可以代替所有关系代词（which,what,who,whom）,而且有几种情况必须使用that：A.先行词是不定代词时；B.先行词受形容词*修饰时；C.当先行词被any, few, little, no, all, much, some等词修饰时D.当先行词为序数词或被序数词所修饰时；E.当先行词被the very, the only, the last, the just, the same等修饰时；F.当先行词既包含人又包含物时当先行词是疑问代词who,which,what或主句以这些词开头时；G.当先行词为主句表语或关系代词为从句表语时.
以下两种情况一般只使用which：在“介词＋关系代词”结构中先行词为“those＋表事物的复数名词”时.
当先行词为时间,地点或方式名词时,就有是使用关系代词和关系副词的问题了.原则非常简单：如果从句主谓宾结构完整,就使用关系副词；如果从句主谓宾结构不完整,使用关系代词.例如:
①This is the place where they met each other for the first time.
这是他们第一次见面的地方.
②This is the place that they will never forgrt.
这是他们永远不会忘记的地方.
在①中,从句部分的主谓宾结构是完整的,因而主句中的“place”充当了从句的地点状语,所以使用了关系副词where；在②中从句中没有宾语,因而主句中的“place” 充当了从句的宾语,所以使用了关系代词that.
注意定语从句中有一类非限制性定语从句.非限制性定语从句是先行词的附加说明,去掉了也不会影响主句的意思,它与主句之间通常用逗号分开,例如：
This is the house which we bought last month. 这是我们上个月买的那幢房子.（限制性）
The house, which we bought last month, is very nice.这幢房子很漂亮,是我们上个月买的.（非限制性）
2) 当先行词是专有名词或物主代词和指示代词所修饰时,其后的定语从句通常是非限制性的,例如：
My house, which I bought last year, has got a lovely garden. 我去年买的的那幢房子带着个漂亮的花园.
3) 非限制性定语从句还能将整个主句作为先行词, 对其进行修饰, 这时从句谓语动词要用第三人称单数,例如：
He seems not to have grasped what I meant, which greatly upsets me. 他似乎没抓住我的意思,这使我心烦.
Liquid water changes to vapor, which is called evaporation. 液态水变为蒸汽,这就叫做蒸发.
说明：关系代词that和关系副词why不能引导非限制性定语从句.
状语从句
状语从句的种类最多,知识点比较零散,归纳之后有以下几种：
时间状语从句
引导词：when, as, while, as soon as, while, before, after, since, till, until, the minute, the moment, the second, every time, the day, the instant, immediately , directly, no sooner … than,hardly …when, scarcely … when
例：
I didn't realize how special my father was until I was 18.
While Tom was watching TV, his wife was reading.
No sooner had I arrived home than it began to rain.
Every time I take your advice, I get into trouble.
地点状语从句
引导词：where, wherever, anywhere, everywhere
Generally, air will be heavily polluted where there are factories.
Wherever you go, you should bring the mp3 player with you.
原因状语从句
引导词：because, since, as, since, seeing that, now that, in that, considering that, given that, considering that, in as much as, in so much as
Now that everybody has come, let's begin our clas.
Considering that he is no more than 10 years old, his height of 1.60 m is not normal.
目的状语从句
引导词：so that, in order that, lest, in case, for fear that, in the hope that, for the purpose that, to the end that
The boss asked his secretary to give him the letter so that he could send it out himself.
The instructor raised his voice that the students at the back could hear more clearly.
结果状语从句
引导词：so … that, so… that, such … that, such that, to the degree that, to the extent that, to such a degree that,
He got up so early that he caught the first train.
It's such a good chance that we must not miss it.
条件状语从句
引导词：if, unless, as/so long as, only if, providing/provided that, suppose that, in case that, on condition that
You will certainly succeed so long as you keep on trying.
Provided that there is no opposition, we shall call off the meeting.
让步状语从句
引导词：though, although, even if, even though, as(用在让步状语从句中 必须要倒装),while ( 一般用在句首 ),no matter …, in spite of ,the fact that, while, whatever, whoever, wherever,whenever, however, whichever
Much as I respect him, I can't agree to his proposal.
No matter how hard he tried, she could not change her mind.
比较状语从句
引导词：as(同级比较), than(不同程度的比较), 特殊引导词：the more … the more … ; just as …, so…; A is to B what /as X is to Y; no … more than; not A so much as B
She is as bad-tempered as her mother.
The house is three times as big as ours.
The more you exercise, the healthier you will be.
Food is to men what oil is to machine. 食物之于人,犹如油之于机器.
方式状语从句
引导词：as, as if, how, the way
When in Rome, do as the Roman do.
She behaved as if she were the boss.
Sometimes we teach our children the way our parents have taught us.
应当注意的知识点有：
引导时间状语从句的连词
主要有when, while, as, by the time, before, after, since, till/until, as soon as等.其中when、while和as都可表示"当……时候",但用法有区别:
1) when意为"在……时;当……时",可表示"点时间"或"段时间",从句谓语可以 是终止性动词,也可以是延续性动词.例如: When I got home, he was having supper.
2) as意为"边……边……"或"与……同时",重在表示两个动作同时发生、伴随进行.as从句是终止性动词时,主句通常也必须是终止性动词.例如: They sang as they danced.
3) while只可表示"段时间",从句谓语只限于延续性动词.例如: While I was sleeping, my father came in.
引导原因状语从句的连词
原因状语从句一般由because, since, as, for引导. 注意as, because, since 和for的区别:
1) 如果原因是构成句子的最主要部分, 一般用because.because引导的从句一般不放在句子的开头.例如: I missed the train because I got up late.
注:对于以why开头的问句, 一般只能用because引导的从句来回答.
2) 如果原因已为人们所知, 或不如句子的其余部分重要, 就用as或since、since 比as稍微正式一些.as和since引导的从句一般放在句子的开头.例如:
As he was not well,I decided to go there without him.
Since this method doesn't work, let's try another.
3) for表示所说的理由是一种补充说明,因此,for引导的从句可以放在括号里,而
且for引导的从句一般不放在句子的开头.例如: I decided to stop and have lunch, for I was feeling quite hungry.
引导结果状语从句的连词
主要有so/such…that…,so that等.
1) so...that结构在某种情况下可以与enough to和too...to结构相互转换.例如:
She is so short that she can't reach the buttons of the lift.
=She is too short to reach the buttons of the lift.
2)so that也可以引导结果状语从句,意为"结果是;以致于".例如: They missed the bus so that they were late for class.
注:so that也可引导目的状语从句, 此时可用to或in order to替换, 将其改为简单句.
例如: He got up early so that he could get to school on time.
=He got up early to get to school on time.
=In order to get to school on time,he got up early .
主语从句
主语从句主要有三类：
由连词that引导的主语从句. 例如：That you will win the medal seems unlikely.
你想获得奖牌看起来是不可能的.
用连接代词which或连接副词if, whether 引导的主语从句. 例如：
Which of them escaped from the * is still a mystery.
他们哪一个是从*里逃跑的,仍然是个谜.
When they will come hasn’t been made pubic.
他们什么时候来还不知道.
Whether she is coming or not doesn’t matter too much.
她来不来都无关紧要.
用关系代词（what,whatever,who,whoerver）引导的主语从句.
主语从句可以直接放在主语位置上,也可以用it作形式主语, 而将从句放在句末（尤其是当谓语较短时）.
当what引导的主语从句表示“…的东西”时,一般不用it作形式主语.
错:It is a book what he wants.
对:What he wants is a book. 他想要的是本书.
如果带主语从句的句子是疑问式,则必须用it作形式主语的结构.
例如：Has it been settled who will be sent to carry out the task ?
谁将被派去执行这项任务决定了吗 ?
固定用法：It is +名词+从句；It is +形容词+从句；It is +过去分词+从句；It +不及物动词+从句(当“及物动词 + 宾语”较短时,也可用这种结构);It +某些固定结构+ 主语从句.
同位语从句
在复合句中用作同位语的从句叫同位语从句.它一般跟在某些名词后面,用以说明该名词表示的具体内容.如： I heard the news that our team had won．我听到了我们队获胜的消息.
可以跟同位语从句的名词通常有news,idea,fact,promise,question,doubt,thought,hope,message,suggestion,words（消息）,possibility等.
英语中引导同位语从句的词有连词 that,whether,连接副词 how,when,where等.（注：if,which 不能引导同位语从句.）如：I have no idea when he will be back．我不知道他什么时候回来.
有时同位语从句可以不紧跟在说明的名词后面,而被别的词隔开.如：The thought came to him that maybe the enemy had fled the city． 他突然想起可能敌人已经逃出城了.
这是我教学中总结的,学生们反映还不错,有什么不明白的再问我.