语法课条件句Conditiona.ppt
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1、条件句 Conditional条件句的结构:条件状语分句+主句第一种类型:真实条件句第一种类型:真实条件句 Real Conditional Real Conditional1.表示普遍真理和客观事实 Eg:If you heat ice,it melts.If you pour oil on water,it floats.由上述诸例可以看出,凡表示不受时间限制的自然法则的条件句,其从句和主句的谓语动词都用一般现在时:(If)simple present+(Main)simple (If)simple present+(Main)simple presentpresent2.表示现在习惯的动
2、作 Eg:If I make a promise,I keep it.If it rains,I go to work by car.在上述表示现在习惯动作的条件句中,从句和主句的谓语动词也都是用一般现在时:(If)simple present+(Main)simple present(If)simple present+(Main)simple present3.表示过去习惯动作 Eg:If I was hungry,I usually had a full meal.If I made a promise,I kept it.在上述表示过去习惯动作的条件句中,从句和主句的谓语动词都用一般过
3、去时:(If)simple past+(Main)simple past(If)simple past+(Main)simple past第二种第二种类型:真型:真实条件条件语句的主体句的主体这种句式可分为:“基本形式”(Basic Form),“变体形式”(Variant Form)和“替换形式”(Alternative Form)1.基本形式基本形式(Basic Form)Eg:If it is fine tomorrow,we can have a picnic somewhere.If you wake up before me,give me a call.从上述诸例可以看出,这一类
4、型条件语句有两个基本形式:一是从句用一般现在时表示将来时间,主语用shall/will/can/may 等+不定式:(If)simple present+(Main)shall/will,etc+inf(If)simple present+(Main)shall/will,etc+inf二是从句用一般现在时表示将来时间,主句用动词祈使式:(If)simple present+(Main)imperative(If)simple present+(Main)imperative2.2.变变体形式体形式(Variant Form)(Variant Form)这种形式又有三种分类从句动词不管主语的人
5、称和数如何,一律用 should+不定式,主句动词可根据语义意图采用不同形式。Eg:If it should rain again,the flowers will bloom.If I should be detained,start the program without me.在这里,should 仅表示一种不太肯定的婉转口气,并不影响条件的真实性。在if-分句中用“will+不定式”并不单纯表示将来意义,这里的 will 是个表示“意愿”的情态助动词,相当于 be willing to Eg:If you will reserve seats,we shall be sure of a
6、 comfortable journey.If he will accept the nomination(提名),a lot of electors will vote for him.要知道这种带“will+不定式”的if-分句在某些场合是不可以随便用的,比如我们可以说:If he gets my letter in time,hell be able to change his plans.却不可以说:If he will get me letter in time,hell be第二种类型:真实条件语句的主体第二种类型:真实条件语句的主体第二种类型:真实条件语句的主体第二种类型:真实条
7、件语句的主体在if-分句中用 would,有表示“意愿”的意思,常用语客气的请求,这时,主句动词既可以用 will/shall+不定式,也可用 would/should/could/might+不定式 Eg:If you would kindly wait a moment,Ill see what I can do.If you would try Italian food,you would like it.如果表示“意愿”的would不是用于客气的请求,那么,在一定上下文中也可能表示不大可能实现的“意愿”,这就属于非真实条件句,即第三种类型的条件句的一种变体形式。3.3.替替换形式形式(
8、Alternative Form)(Alternative Form)Set your alarm clock,and you wont oversleep.=If you set your alarm clock,you wont oversleep.Set your alarm clock,or(else)youll oversleep.=If you dont set your alarm clock,youll oversleep.第三种类型:非真实条件句第三种类型:非真实条件句 Unreal Conditional Unreal Conditional基本形式:(If)simple
9、past/were+(Main)would,etc+infEg:If we caught the 10 oclock train,we would(could,might,etc)get there by lunch-time.if-分句说表示的条件在说话人看来实现的可能性不大,但还是有可能的,比如说话时间已经是九点多钟,尚未动身,因而不大可能赶上十点钟的火车,也不大可能在吃午饭以前到达。If I came into a fortune,I would give up working.if-分句表示的条件came into fortune 显然是一种主观臆想,几乎不可能实现。If I knew
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