if的基本释义为如果、即使、是否。那么你对if的使用方法了解多少呢?以下是由小编整理关于if的用法的内容，希望大家喜欢!

if的用法

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

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.

if的单词资料

发音

英 [ɪf] 美 [ɪf]

释义

conj. (表条件)如果;即使;是否;(表假设)假如

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。

n. 条件;设想

There are too many ifs in his offer.

他的提议中条件太多了。

缩写

IF=i.f.

if.

缩写词 abbr.

1. =information feedback 信息回馈

2. =interferon

3. =intermediate frequency 中频

i.f.

缩写词 abbr.

=intermediate frequency 中频

if的扩展知识

1. if和whether在宾语从句中，都表“是否”，可换用，if更口语化，whether正式些。

当有or not时， 一般用whether，而不用if。

He wants to know if/whether you can help him.

She wonders whether you'll go or not.

2. if可引起条件状语从句，whether不用于状语从句。

If you work hard, you'll succeed.

If I were you , I would do it in another way.

3. whether可引起主语从句，表语从句，if不能用于这两种情况。

Whether you can finish it in time or not depends on yourself.

The question is whether they'll help you.

4. if在名词性从句中只能引导动词后的宾语，whether可通用。