if的用法總結(jié)
if的用法總結(jié)
以下是小編為大家整理的if句型的用法總結(jié)，希望能幫助大家更好地認(rèn)識(shí)if句型，提高英語水平。
if的意思和用法：
conj.如果，倘若; 即使; 〈口〉是否; 假設(shè);
n.條件，設(shè)想;
1. (表示條件)如果 ,主句用將來時(shí)，if從句用現(xiàn)在時(shí)表示將來
He will come if you invite him.
如果你請(qǐng)他,他會(huì)來的。
2. (表示虛擬)假如,要是
1)時(shí)態(tài)：可以表示過去，現(xiàn)在和將來的情況。它的基本特點(diǎn)是時(shí)態(tài)退后。
a. 同現(xiàn)在事實(shí)相反的假設(shè)。
句型 ： 條件從句主句
一般過去時(shí)should( would) +動(dòng)詞原形
If they were here, they would help you.
b. 表示于過去事實(shí)相反的假設(shè)。
句型： 條件從句主句
過去完成時(shí)should(would) have+ 過去分詞
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(duì)將來的假想
句型： 條件從句主句
一般過去時(shí)should+ 動(dòng)詞原形
were+ 不定式would + 動(dòng)詞原形
should+ 動(dòng)詞原形
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 連接賓語從句
I wonder if she is ill.
不知她是否病了。
連接詞 conj.
1.(表示條件)如果
He will come if you invite him.
如果你請(qǐng)他,他會(huì)來的。
2.(表示虛擬)假如,要是
If I were you, I would never do that.
如果我是你,我決不做那件事。
3.(表示讓步)即使
We'll go even if it rains.
即使下雨我們也要去。
4.是否
I wonder if she is ill.
不知她是否病了。
5.(表示因果關(guān)系)每一次...的時(shí)候(總是會(huì))
If I feel any doubt, I inquire.
我一感到有疑問就隨時(shí)詢問。
if作為連詞的時(shí)候，一般用于條件狀語從句或者是賓語從句或讓步狀語從句
if引導(dǎo)的條件狀語從句：If he comes, please tell me.(如果，假如)
主句和從句位置可以互換，時(shí)態(tài)：主將從現(xiàn)
變成：Please tell me,if he comes.
賓語從句中：I want to know if(是否) he comes.
可改成：I want to know whether he comes.
當(dāng)句子中有or not是 只能用whether——I want to know whether he comes or not.
if句型的時(shí)態(tài)：
1.主過從過
2.主句一般現(xiàn)在時(shí)，從句任何時(shí)
3.客觀真理用一般現(xiàn)在時(shí)
讓步狀語從句中，if 解釋為即使
名詞 cn. 條件;設(shè)想
There are too many ifs in his offer.
他的提議中條件太多了
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