一、語氣的定義和種類
l、語氣：語氣是動詞的一種形式，它表示說話人對某一行為或事情的看法和態度。
2、語氣的種類：
(1)陳述語氣: 表示動作或狀態是現實的、確定的或符合事實的，用于陳述句、疑問句和某些感嘆句。如：We are not ready. 我們沒準備好。What a fine day it is!多好的天氣啊!
(2)祈使語氣: 表示說話人的建議、請求、邀請、命令等。如: Open the door, please。請打開門。
(3)虛擬語氣: 表示動作或狀態不是客觀存在的事實，而是說話人的主觀愿望、假設或推測等。如: If I were you, I should study English. 如果我是你，我就學英語了。May you succeed! 祝您成功！
二、虛擬語氣在條件從句中的用法
條件句有兩類，一類是真實條件句，一類是虛擬條件句。如果假設的情況是有可能發生的，就是真實條件何。在這種真實條件句中的謂語用陳述語氣。如: If it doesn’t rain tomorrow, we will go to the park. 如果明天不下雨，我們就去公園。
如果假設的情況是過去或現在都不存在的，或將來不大可能發生的，則是虛擬條件句。如: If he had seen you yesterday, he would have asked you about it. 如果他昨天見到你，他會問你這件事的。(事實上他昨天沒見到你，因此也未能問你這件事。)
在含有虛擬條件句的復合句中，主句和從句的謂語都要用虛擬語氣。現將虛擬條件從句和主句的動詞形式列表如下:
從 句 主 句
與現在事實相反 動詞的過去式（be的過去式一般用were） would/ should/ could/ might + 動詞原形
與過去事實相反 had + 過去分詞 would/ should/ could/ might + have + 過去分詞
與將來事實相反 動詞過去式，should + 動詞原形，were to + 動詞原形 would/ should/ could/ might + 動詞原形
注: 主句中的should只用于I、we，但在美國英語中，should常被would代替；從句中的should 可用于各種人稱。
l、表示與現在事實相反的假設和結果。如: If my brother were here, everything would be all right. 要是我哥哥在這兒 ，一切都沒問題了。
2、表示與過去事實相反的假設和結果。如: If you had taken my advice，you wouldn't (couldn’t) have failed in the exam. 如果你按照我的建議去做，你一定不會(不可能)考試不及格。
3、表示與將來事實可能相反的假設和結果。如: If it were Sunday tomorrow, I should (would，could，might) go to see my grandmother. 如果明天是星期天，我就 (可能)去看望我奶 奶。If it were to snow this evening, they would not go out. 如果今晚下雪，他們將不出去了。
4、有時條件從句中的動作和主句中的動作發生的時間不一致（表示錯綜時間的虛擬語氣），這時動詞的形式要根據它所表示的時間加以調整。例如: If you had listened to the doctor, you would be all right now. 如果你當初聽了醫生的話，身體現在就好了。(從句動作指過去，主句動作指現在)
5、虛擬條件句可以轉換成下列形式:
(l)省略連詞if。在書面語中，如果虛擬條件從句中有were，had 或 should，可以把if省略，把這幾個詞放到主語之前，構成主謂倒裝。例如: Should he come (If he should come), tell him to ring me up. 他要是來了，讓他給我打個電話。Were I you (If I were you), I would not do it. 我要是你，就不做這事。
(2)用介詞短語代替條件狀語從句。有時假設的情況并不用條件從句表示出來，而是通過介詞短語來表示。如: Without air (If there were not air), there would be no living things. 如果沒有空氣的話，就不會有生物了。But for your help (If it hadn’t been for your help) I couldn’t have done it. 要是沒有你的幫助，我就不可能完成這件事。
假設的情況有時可以通過上下文或其他方式表現出來。如: I was busy that day. Otherwise I would have gone there with them. (If I hadn’t been busy that day, I would have gone there with them.) 我那天很忙，否則，我就和他們一起去那兒了。(如果我那天不忙的話，我就……)；I would have finished the work, but I have been ill. (If I hadn’t been ill, I would have finished the work.) 我本來該完成這項工作的，但我生病了。(如果我沒生病的話，我就會完成……)
6、省去條件從句或主句：表示虛擬語氣的主句或從句有時可以省略，但其含義仍可以推知。
(1)省去條件從句。如: You could have washed your clothes yourself. 你本可以自已洗衣服的。省去了"If you had wanted to")(事實是:你自己沒洗衣服，因為你不想洗。)
(2)省去主句(常用以表示愿望)。如: If my grandmother were with me! 如果我的祖母與我在一起多好啊!(事實是:祖母已不在世。)；If only she had not left! 如果她沒走就好了!(事實是:她已經走了。)
三、虛擬語氣的其他用法
l、虛擬語氣在主語從句中的用法：在"It is important (strange，natural，necessary)that…"這類句型里，that所引導的主語從句中的謂語動詞常用 “should十動詞原形”結構，表示某事是"重要"、"奇怪"、"自然"、"必要"等意義。如: It is important that every member (should) inform himself of these rules. 重要的是每個成員知道這些規則。
2、虛擬語氣在賓語從句中用法：
(1)在動詞wish后的賓語從句中，表示與現在或過去的事實相反，或對將來的主觀愿望，從句通常省略連詞that。1)表示對現在情況的虛擬:從句動詞用過去式或過去進行式(be動詞一般用were)。如: I wish I knew the answer to the question. 我希望知道這個問題的答案。(可惜不知道)；2）表示對過去情況的虛擬:從句動詞常用"had十過去分詞"。如: I wish (wished) I hadn’t spent so much money. 我后悔不該花那么多錢。(實際上已經花掉)；3)表示對將來的主觀愿望:謂語動詞形式為"would十動詞原形"。此時要注意，主句的主語與從句的主語不能相同，因為主句的主語所期望的從句動作能否實現，取決于從句主語的態度或意愿(非動物名詞除外)。如: I wish it would stop raining. 但愿雨能停止；I wish you would come soon. 但愿你立刻來。
(2)在suggest，demand，order，propose，insist，command，request，desire等動詞后的賓語從句中，謂語動詞用“should + 動詞原形”，表示建議、要求、命令等。如: I demand that he (should) answer me immediately. 我要求他立刻答復我。
3、虛擬語氣在狀語從句中的用法
(1)在帶有even if/ even though引導的讓步狀語從句的主從復合句中，主句和從句都用虛擬語氣，動詞形式與含有非真實條件句的虛擬語氣相同。如: Even if he had been ill, he would have gone t his office. 即使生了病，他倆去辦公室。
(2)由as if或as though引導的狀語從句表示比較或方式時。從句謂語形式為動詞的過去式(be用were)或 “had十過去分詞”。如: He treated me as if I were a stranger. 他那樣對待我，好像我是陌
生人似的。She talked about the film as if she had really seen it. 她談論那部影片，就好像她確實看過一樣。
注:如果表示的事情可能會發生，那么方式狀語從句中的謂語動詞可用陳述語氣。
(3)在in order that或so that引導的目的狀語從句中，謂語動詞多用 “could或might（有時也用should）+ 動詞原形”。如: Mr green spoke slowly so that his students could (might) hear clearly. 格林先生說得很慢，好讓學生聽清楚。
4、虛擬語氣在定語從句中的用法：在"It is time (that) …"句型中，定語從句的謂語動詞常用虛擬語氣表示將來，動詞形式一般用過去式，意思是"該干某事的時候了"。如: It’s (high) time we did our homework. 我們該做作業了。
5、虛擬語氣在簡單句中的用法
(1)情態動詞的過去式用于現在時態時，表示說話人的謙虛、客氣、有禮貌，或委婉的語氣，常見于日常會話中。如: It would be better for you not to stay up too late. 你最好別太晚睡覺。
(2)在一些習慣表達中。如: I would rather not tell you. 我寧愿不告訴你。
(3)用“may + 動詞原形”表示"祝愿"、"但愿”，此時may須置于句首（多用于正式文體中）。如：May you be happy!祝你快樂！May good luck be yours.祝你順利。
練習、虛擬語氣
1. If I ____ where he lived, I ____ a note to him.
A. knew, would B. had known, would have sent
C. know, would send D. knew, would have sent
2. If they ____ earlier than expected, they ____ here now.
A. had started, would be B. started, might be
C. had started, would have been D. will start, might have been
3. I didn’t know his telephone number. ____ it, I ____ then.
A. Had I known, would ring him up B. Should I know, would have rung him up
C. If I knew; would ring him up D. Had I known; would have rung him up
4. Mary is ill today. If she _____ , she ____ absent from school.
A. were not ill; wouldn' t be B. had been ill; wouldn't have been
C. had been ill; should have been D. hadn't been ill; could be
5. Were I to do it, I ________ it some other way.
A. will do B. would do C. would have done D. were to do
6. I ________ him the answer ________ possible, but I was so busy then.
A. could tell; if it had been B. must have told; were it
C. should have told; had it been D. should have told; should it be
7. Without your help, we________ so much.
A. won ' t achieve B. didn ' t achieve
C. don't achieve D. wouldn't have achieved
8. You didn't take his advice. ________ his advice, you ________ such a mistake.
A. Had you taken; wouldn't have made B. If you had taken; would make
C. Were you lo take; shouldn t have made D. Have you taken; won t have made
9. We wish we ____ what you did when we were at high school.
A. did B. could have done C. have done D. should do
10. She wishes she ____ to the theatre last night.
A. went B. would go C. had gone D. were going
11. Tom is very short now. His mother wishes that he ________ be tall when he grows up.
A. could B. should C. would D. were able to
12. My sister advised me that I ________ accept the invitation.
A. could B. must C. should D. might
13. He asks that he ________ an opportunity to explain why he’s refused to go there.
A. is given B. must give C. should give D. be given
14. Do you think of Wang Fang's suggestion that he ________ Mr. Li to the party?
A. will invite B. have invited C. is invited D. invite
15. I insisted that he ________ at once.
A. be gone B. go C. would go D. might go
16. Li Ming insisted that he ________ anything at all.
A. hadn ' t stolen B. shouldn ' t steal C. doesn ' t steal D. steal
17. It is quite natural that my coming late again ________ them very angry.
A. had made B. would make C. makes D. make
18. He acted as if he ________ everything in the world.
A. knew B. knows C. has known D. won't know
19. Read it aloud so that I ________ you clearly.
A. may hear B. will hear C. hear D. have heard
20. They got up early in order that they ________ they first train.
A. caught B. will catch C. might catch D. shall catch
21. I am sorry that he ________ in such poor health.
A. are B. shall be C. were D. should be
22. That is a good book. You ________ it yesterday.
A. could buy B. should buy C. should have bought D. bought
23. It is high time we ________ home.
A. will go B. would go C. have gone D. went
24. I ' d rather that you ________ home.
A. went B. have gone C. will go D. had gone
25. If only I _________ to the lecture!
A. listen B. will listen C. am listening D. had listened
26. ---- If he_____ , he ______ that food. ---- Luckily he was sent to the hospital immediately.
A. was warned; would not take B. had been warned; would not have taken
C. would be warned; had not taken D. would have been warned; had not taken
27.I didn' t see your sister at the meeting. If she _________, she would have met my brother.
A. has come B. did come C. came D. had come
28. Without electricity, human life ________ quite different today.
A. is B. will be C. would have been D. would be
29. He ________ you more help, even though he was very busy.
A. might have given B. might give C. may have given D. may give
30. If city noises _______ from increasing, people _______ shout to be heard even at the dinner table 20 years from now.
A. are not kept; will have to B. are not kept; have to
C. do not keep; will have to D. do not keep; have to
31. Mike's father, as well as his mother, insisted that he ________ home.
A. stayed B. could stay C. has stayed D. stay
32. Mr. Smith insisted that he ________ the work all.
A. had done B. have done C. did D. so
33. Jane would never have gone to the party ________ that Mary would come to see her.
A. has she known B. had she known C'. if she know D. if she has known
34. If you had enough money, what ________ ?
A. will you buy B. would you buy C. would you have bought D. will you have bought
35. If you ________ that film late last night, you wouldn't be so sleepy.
A. didn't see B. haven't seen C. wouldn’t have seen D. hadn’t seen
36. Our monitor requested that ________.
A. all the class studied more carefully the problem
B. the problem was more carefully studied
C. with great care the problem could be studied
D. all the class study the problem more carefully
37. ---- Would you have called her up had it been possible?
---- Yes, but I ________. busy doing my homework..
A. was B. were C. had been D. would be
38. His tired face suggested that he ________ really tired after the long walk.
A. had been B. was C. be D. should be
39. It is important that we ________.
A. shall close the window before we leave B. will close the window before we leave
C. must close the window before we leave D. close the window before we leave
40. I didn't know his telephone number, otherwise I ______ him.
A. had telephoned B. would telephone C. would have telephoned D. telephone