if條件狀語從句時態口訣;if條件狀語從句的三種時態

當假設是不大可能實現時,就是虛擬條件句，常用if來引導，根據對假設的可能發生的事情是發生在過去、現在、將來總結如下：

(1) 與過去事實相反：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. 如果她再努力一點，她就會成功的。

The rice would not have been burnt if you had been more careful. 如果你再小心一點，米飯就不會燒焦了。

If my lawyer had been here last Saturday,he would have prevented me from going. 如果我的律師上周六來過這里，他會阻止我去的。

If he had come yesterday,I should / would have told him about it. 如果他昨天來的話，我應該/本應該把這件事告訴他。

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. 如果他沒有生病，錯過許多課程，他會取得更大的進步。

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

例：If the man had pointed with his first finger while he was in Brunei, everyone would have thought that he was very rude.

如果這個人在文萊的時候用他的第一個手指指著他，每個人都會認為他很粗魯。

(2) 與現在事實相反：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. 如果他們在這里，他們會幫助你。

If I were in your position, I would call the police immediately.

如果我處在你的位置，我會立即打電話給**。

(3) 與將來事實相反：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. 如果你成功了，一切都會好起來的。

If you should succeed,everything would be all right. 如果你成功了，一切都會好起來的。

If you were to succeed,everything would be all right. 如果你成功了，一切都會好起來的。

If I should have time tomorrow, I would certainly help you.

如果我明天有空的話，我當然會幫助你的。

(4) 虛擬條件句中的倒裝：(如果省去if，則要用倒裝語序)

例：Should it rain, the crops would grow better.

如果天下雨的話，莊稼會長得更好。

Were I your father, I would not give you the money.

如果我是你父親的話，我就不會給你那錢了。

Had it not been for the captain, the ship would have sunk如果不是那船長的話，那船就會沉沒了

知識拓展：

1.if (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. “后退一步法”

后退一步法是指在準確地判斷了該句與哪一事實相反后,按虛擬語氣的后退一步法處理從句謂語動詞的時態.即：在非真實條件狀語從句中,謂語動詞按正常情況“后退一步”.也就是：

①與過去事實相反,在從句中用過去完成時形式表示.

②與現在事實相反,在從句中用過去一般時形式表示.

③與將來事實可能相反,在從句中用過去將來時形式表示.

主句中則用情態動詞would,should,could 等加一個與從句一致的動詞形式.例：

⑴、If I had come her yesterday,I would have seen him.

如果我昨天來的話，我會見到他的。

⑵、If I were a teacher,I would be strict with my students.

如果我是一名教師，我會嚴格要求我的學生。

⑶、If it should snow tomorrow,they couldn't go out.

如果明天下雪，他們就不能出去了。