if的用法总结
以下是小编为大家整理的if句型的用法总结，希望能帮助大家更好地认识if句型，提高英语水平。
if的意思和用法：
conj.如果，倘若; 即使; 〈口〉是否; 假设;
n.条件，设想;
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
1)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
The rice would not have been burnt if you had been more careful.
If she had worked harder, she would have succeeded.
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 were to succeed, everything would be all right.
If you should 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。
连接词 conj.
1.(表示条件)如果
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
If I were you, I would never do that.
如果我是你,我决不做那件事。
3.(表示让步)即使
We'll go even if it rains.
即使下雨我们也要去。
4.是否
I wonder if she is ill.
不知她是否病了。
5.(表示因果关系)每一次...的时候(总是会)
If I feel any doubt, I inquire.
我一感到有疑问就随时询问。
if作为连词的时候，一般用于条件状语从句或者是宾语从句或让步状语从句
if引导的条件状语从句：If he comes, please tell me.(如果，假如)
主句和从句位置可以互换，时态：主将从现
变成：Please tell me,if he comes.
宾语从句中：I want to know if(是否) he comes.
可改成：I want to know whether he comes.
当句子中有or not是 只能用whether——I want to know whether he comes or not.
if句型的时态：
1.主过从过
2.主句一般现在时，从句任何时
3.客观真理用一般现在时
让步状语从句中，if 解释为即使
名词 cn. 条件;设想
There are too many ifs in his offer.
他的提议中条件太多了
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if的用法
