if的用法總結
以下是小編爲大家整理的if句型的用法總結，希望能幫助大家更好地認識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;
n.條件，設想;
1. (表示條件)如果 ,主句用將來時，if從句用現在時表示將來
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
1)時態：可以表示過去，現在和將來的情況。它的基本特點是時態退後。
a. 同現在事實相反的假設。
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. 表示於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
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 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.
如果你請他,他會來的。
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.(表示因果關係)每一次...的時候(總是會)
If I feel any doubt, I inquire.
我一感到有疑問就隨時詢問。
if作爲連詞的時候，一般用於條件狀語從句或者是賓語從句或讓步狀語從句
if引導的條件狀語從句：If he comes, please tell me.(如果，假如)
主句和從句位置可以互換，時態：主將從現
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句型的時態：
1.主過從過
2.主句一般現在時，從句任何時
3.客觀真理用一般現在時
讓步狀語從句中，if 解釋爲即使
名詞 cn. 條件;設想
There are too many ifs in his offer.
他的提議中條件太多了
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if的用法
