英語if的用法歸納
IF是一個英語單詞，名詞、連詞，作名詞時意思是“條件，設想；不確定的情況”，作連詞時意思是“（表條件）如果；（表假設）要是，假如；無論何時；雖然，即使；（用于間接疑問）是否；（用于禮貌問詢）是否；當，每次；（與情態(tài)動詞連用）表婉轉(zhuǎn)客氣；這不是……，要是……多好；或許不；就算；盡管”。以下是小編為大家?guī)淼挠⒄Zif的用法歸納，希望能幫助到大家。
英語if的用法歸納 篇1
if從句和虛擬語氣:
1. 當if后面接一般現(xiàn)在時的動詞時,表示對將來的一種推測. if sb do sth sb will/shall do sth. If you go with me,you shall be rewarded.
2. 當if后面接一般過去時的動詞時,則是一種虛擬語氣. 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. 當if后面接什么時態(tài)都可以時，if為“是否”的意思，句子為賓語從句. sb do sth if sb do sth. He said if rain was stop. 由if引導的條件狀語從句，時態(tài)應該是主將從現(xiàn)，就是說主句用一般將來時，而從句用一般現(xiàn)在時表示將來。
例如 If it doesn't rain tomorrow,I will visit my former school. 這里從句就用一般現(xiàn)在時。當然if引導的從句也可以用虛擬語氣，例如 If I got up early in the morning,I wouldn't miss the train.
If 引導的條件狀語從句大盤點
一. 條件狀語從句表示主句動作發(fā)生的條件.引導條件狀語從句的連詞不多,初中階段最常用的引導詞為If(如果).切記：引導條件狀語從句的If,不能用whether來替換.例句：
(1)Please call me if he is at home.(假如他在家,請給我打電話.)
(2)You must see a doctor if you are ill.(如果你生病了,就必須去看醫(yī)生.)
(3)Don’t go to the beach if it rains.(倘若下雨就不要去海灘了.)
(4)If it rains tomorrow,I won’t go there with you.(如果明天下雨的.話,我就不和你一起去那兒了.)
二.條件狀語從句的時態(tài)：
1.主句用一般將來時,條件狀語從句用一般現(xiàn)在時表將來.如：例句(4)
2.當主句含情態(tài)動詞時,條件狀語從句用一般現(xiàn)在時.如：例句(2)
3.當主句為祈使句,條件狀語從句用一般現(xiàn)在時.如：例句(1)和 (3)
三.正確區(qū)分If 引導的條件狀語從句和If 引導的賓語從句
在賓語從句中If為“是否”,如表示“將來”時,則用將來時態(tài),賓語從句一般位于主句之后;而在條件狀語從句中If的意思為“如果”,主句用一般將來時,從句用一般現(xiàn)在時表將來,且從句位置比較靈活,可位于主句之后也可位于主句之前.請比較：
If you keep on working hard at English,you can learn it well.
如果你繼續(xù)努力學習英語,你就能夠?qū)W好它.(條件狀語從句)
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親是否將帶他去動物園.(賓語從句)
四.If 引導條件狀語從句與祈使句的轉(zhuǎn)換：
主語為you的條件狀語從句還可與“祈使句 + and / or + 簡單句” 句式
互換.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.
英語if的用法歸納 篇2
if的用法有：
1、(表示條件)如果，主句用將來時，if從句用現(xiàn)在時表示將來
He will come if you invite him.
如果你請他，他會來的。
2、(表示虛擬)假如，要是
時態(tài)：可以表示過去，現(xiàn)在和將來的情況.它的基本特點是時態(tài)退后。
a、同現(xiàn)在事實相反的假設。
句型 ：條件從句 主句
一般過去時 should( would) +動詞原形
If they were here,they would help you.
b、表示于過去事實相反的假設。
句型：條件從句 主句
過去完成時 should(would) have+ 過去分詞
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.
含義：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.
含義：He was ill and missed many lessons,so he did not make greater progress.
c、表示對將來的假想
句型：條件從句 主句
一般過去時 should+ 動詞原形
were+ 不定式 would + 動詞原形
should+ 動詞原形
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 連接賓語從句
I wonder if she is ill.
不知她是否病了。
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