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if的用法总结

2019-06-12 15:15:18文/刘美娟

if的用法:表现前提,意义是假如;表现捏造,意义是倘使;表现能否的寄义,跟whether相同用法,衔接宾语从句。

if的用法总结

1.(表现前提)假如 ,主句用未来时,if从句用现在时表现未来

He will come if you invite him.

假如你请他,他会来的.

2.(表现捏造)倘使,假如

时态:可以表现过去,现在跟未来的状况.它的基本特征是时态退后.

a.同现在毕竟相反的假设.

句型 :前提从句 主句

普通过去时 should( would) +动词本相

If they were here,they would help you.

b.表现于过去毕竟相反的假设.

句型:前提从句 主句

过去实现时 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.

寄义: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.

寄义:He was ill and missed many lessons,so he did not make greater progress.

c.表现对未来的想象

句型:前提从句 主句

普通过去时 should+ 动词本相

were+ 不定式 would + 动词本相

should+ 动词本相

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.能否 = whether 衔接宾语从句

I wonder if she is ill.

不知她能否病了.

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