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英语if的用法归纳
IF是一个英语单词，名词、连词，作名词时意思是“条件，设想；不确定的情况”，作连词时意思是“（表条件）如果；（表假设）要是，假如；无论何时；虽然，即使；（用于间接疑问）是否；（用于礼貌问询）是否；当，每次；（与情态动词连用）表婉转客气；这不是……，要是……多好；或许不；就算；尽管”。以下是小编为大家带来的英语if的用法归纳，希望能帮助到大家。
if从句和虚拟语气:
1. 当if后面接一般现在时的动词时,表示对将来的一种推测. if sb do sth sb will/shall do sth. If you go with me,you shall be rewarded.
2. 当if后面接一般过去时的动词时,则是一种虚拟语气. if sb did sth sb would/should do sth. If I didn't make that mistake,I would't have suffered such a failure.
3. 当if后面接什么时态都可以时，if为“是否”的意思，句子为宾语从句. sb do sth if sb do sth. He said if rain was stop. 由if引导的条件状语从句，时态应该是主将从现，就是说主句用一般将来时，而从句用一般现在时表示将来。
例如 If it doesn't rain tomorrow,I will visit my former school. 这里从句就用一般现在时。当然if引导的从句也可以用虚拟语气，例如 If I got up early in the morning,I wouldn't miss the train.
If 引导的条件状语从句大盘点
一. 条件状语从句表示主句动作发生的条件.引导条件状语从句的连词不多,初中阶段最常用的引导词为If(如果).切记：引导条件状语从句的If,不能用whether来替换.例句：
(1)Please call me if he is at home.(假如他在家,请给我打电话.)
(2)You must see a doctor if you are ill.(如果你生病了,就必须去看医生.)
(3)Don’t go to the beach if it rains.(倘若下雨就不要去海滩了.)
(4)If it rains tomorrow,I won’t go there with you.(如果明天下雨的.话,我就不和你一起去那儿了.)
二.条件状语从句的时态：
1.主句用一般将来时,条件状语从句用一般现在时表将来.如：例句(4)
2.当主句含情态动词时,条件状语从句用一般现在时.如：例句(2)
3.当主句为祈使句,条件状语从句用一般现在时.如：例句(1)和 (3)
三.正确区分If 引导的条件状语从句和If 引导的宾语从句
在宾语从句中If为“是否”,如表示“将来”时,则用将来时态,宾语从句一般位于主句之后;而在条件状语从句中If的意思为“如果”,主句用一般将来时,从句用一般现在时表将来,且从句位置比较灵活,可位于主句之后也可位于主句之前.请比较：
If you keep on working hard at English,you can learn it well.
如果你继续努力学习英语,你就能够学好它.(条件状语从句)
My little brother wants to know if my father take him to the zoo on Sunday.
我的小弟弟想知道星期天我父亲是否将带他去动物园.(宾语从句)
四.If 引导条件状语从句与祈使句的转换：
主语为you的条件状语从句还可与“祈使句 and / or 简单句” 句式
互换.例如：If you work harder,you’ll pass the exam.=Work harder,and you’ll pass the exam.
If you don’t hurry up,you’ll miss the train.=Hurry up,or you’ll miss the train.
if的用法有：
1、(表示条件)如果，主句用将来时，if从句用现在时表示将来
He will come if you invite him.
如果你请他，他会来的。
2、(表示虚拟)假如，要是
时态：可以表示过去，现在和将来的情况.它的基本特点是时态退后。
a、同现在事实相反的假设。
句型 ：条件从句 主句
一般过去时 should( would) 动词原形
If they were here,they would help you.
b、表示于过去事实相反的假设。
句型：条件从句 主句
过去完成时 should(would) have 过去分词
If she had worked harder,she would have succeeded.
The rice would not have been burnt if you had been more careful.
If my lawyer had been here last Saturday,he would have prevented me from going.
If he had come yesterday,I should / would have told him about it.
含义：He did not come yesterday,so I did not tell him about it.
If he had not been ill and missed many classes,he would have made greater progress.
含义：He was ill and missed many lessons,so he did not make greater progress.
c、表示对将来的假想
句型：条件从句 主句
一般过去时 should 动词原形
were 不定式 would 动词原形
should 动词原形
If you succeeded,everything would be all right.
If you should succeed,everything would be all right.
If you were to succeed,everything would be all right.
3、是否=whether 连接宾语从句
I wonder if she is ill.
不知她是否病了。
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