if引導的條件句中的虛擬語氣

1、if引導的條件句中的虛擬語氣虛擬語氣表示一種不能實現(xiàn)的假設(shè)。該語法主要用于if條件狀語從句。一、if引導的條件狀語從句的分類及虛擬條件句的判斷1、可以把條件句分為兩類：1).真實條件句（Sentences of Real Condition）：凡是假設(shè)的情況發(fā)生性可能很大，就是真實條件句。例如：、If I have time , I will help you with this work.如果我有時間會幫助你做此工作的。(2)、If time permits, we'll go fishing together.(如果有時間的話，我們就一起去釣魚。）2).虛擬條件句（Sentence

2、s of Unreal Condition）：當假設(shè)是不大可能實現(xiàn)時，就是虛擬條件句。例如：、If I were you , I would have attended the meeting. 如果我是你的話，就去參加會議了。、If he had come here yesterday, he would have seen his old friend.假如他昨天來這兒的話，就會看見他的老朋友。、If it had rained yesterday, we would have stayed at home.（如果昨天下雨的話，我們就會留在家里。）2、.if條件狀語從句中虛擬語氣的判斷判斷

3、是真實條件句還是非真實條件句。只有在非真實條件句中才使用虛擬語氣。通過句子意思，看假設(shè)的條件是否能夠?qū)崿F(xiàn)，能夠?qū)崿F(xiàn)是真實條件句，不能使用虛擬語氣；假設(shè)的條件不能實現(xiàn)則是非真實條件句，要用虛擬語氣。判斷這個假設(shè)是與哪個事實相反。通常有三種情況：與過去事實相反。與現(xiàn)在事實相反。與將來事實可能相反。3、“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(tài)。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：與過去事實相反，在從句中用過去完成時形式表示。與現(xiàn)在事實相反，在從句中用過去一般時形式表示。與將來事實可能相反，在從句中用過

4、去將來時形式表示。主句中則用情態(tài)動詞would, should, could 等加一個與從句一致的動詞形式。例：、If I had come her yesterday, I would have seen him.、If I were a teacher, I would be strict with my students.、If it should snow tomorrow, they couldn't go out.4、注意事項if條件句中如有were, should, had，可以省去if，并使用倒裝語序。在現(xiàn)代英語中if條件狀與從句中的謂語動詞如果是be其過去形式一般用w

5、ere。二、虛擬語氣在if 引導的條件句中的用法：（一）、表示與現(xiàn)在事實相反的情況。其句子結(jié)構(gòu)為：從句：if + 主語+ 動詞的過去式(be 用were) + 主句：主語+ would (should, could , might) + 動詞原形+ 例：1.If I were you, I would go with him.2.If the weather were fine, I would go there.如果天氣好，我去那兒。（事實天氣不好）3.If I were you, I would read it again.如果我是你的話，我再讀一遍。（事實上我不是你）4.If time

6、permitted, I would write it again.如果時間允許的話，我再寫一遍。（事實上時間不允許）5.If it werent snowing, we wouldnt stay in the house.要是現(xiàn)在不下雪的話，我們就不會待在屋里。（事實上現(xiàn)在下雪）6.What would I do if I were in your place?要是我處于你地位我會怎么辦？（事實上我不在你的位置上）7.If he hurried, he could catch the first bus.他要是快點能夠趕上頭班公共汽車。（可是他不著急）8.If it werent for y

7、our help, we would get into trouble.如果沒有你們的幫助，我們就會陷入困境。（而事實上得到了你們的幫助）9.If we had the manpower, we could open up even more land.如果有人力,我們還能開更多的荒地.10. If I were you, I would go with him.(從句If I were you, 主句I would go with him.)11. If I were you, I should buy it.(從句用過去式動詞were，主句用動詞原形buy)12. If I had time, I would study French.(如果有時間，我會學習法文。）（從句用過去式動詞had，主句用動詞原形study）13. If she knew English, she would not ask me for help.(如果她懂英文，她就不必要我?guī)土恕?(從句用過去式動詞knew, 主句用動詞原形ask)注意：如果動作在進行中，主句要用："