虚拟语气英语中的语气分为陈述语气、祈使语气、虚拟语气三类。
虚拟语气表示说话人的主观愿望或假想，所说的是一个条件，不一定是事实，或与事实相反。
条件句可分为两类，一类为真实条件句，一类为非真实条件句。
非真实条件句表示的是假设的或实际可能性不大的情况，故采用虚拟语气。
如果假设的情况可能发生，是真实条件句，这种情况下谓语用陈述语气。
如：If time permits, we'll go fishing together.如果时间允许，我们就一起去钓鱼。
如果假设的情况是不存在的或不大可能发生的，则是虚拟条件句。
如：If you had come yesterday, you would have met that famous professor.如果你昨天来，你就会见到那位著名的教授了。
（隐含的事实是：你昨天没来，也没见到那位著名教授）。
虚拟语气的基本形式和用法在含有虚拟条件句的复合句中，主从句的谓语都要用虚拟语气。
1. 含有条件状语从句的复合句wish（would rather）+宾语从句suggest（…）+宾语从句2. 主语从句 It is + adj./p.p/n.+ that+ S+ (should) +do表语从句S+is that +s + (should) +do同位语从句 S+that +s +(should) +do3. 定语从句 It is (high) time that + S + did用过去式表现在情况1. 时态后退型用过去完成式表过去两种形式用过去将来表将来2. should+动词原形型内容详述I. 含有条件状语从句的复合句(以do为例;S=主语)时间条件状语从句主句与现在事实相反的假设 If +S+did…S+would/should/could/might+do…与过去事实相反的假设 If +S+had done… S+would/should/could/might+have done…与将来事实相反的假设did…If+S should dowere to doS+would/should/could/might+do…注意事项：1．倒装句。
如果条件句中含有功能词had，should，were时，可以省去If，把功能词提前，构成倒装句。
2．错综条件句。
若条件句和主句动作不存在同一个时间，则谓语形式应根据具体情况而定。
3．If there weren't/had not been +…=without…4．If it were not for…/ If it hadn't been for…= but for…5．otherwise+虚拟语气的句子6．虚拟语气的句子，but+ 陈述事实的句子II. 虚拟语气用在宾语从句中sb. did …(希望现在用过去式)1. wish+that sb. had done…（希望过去用过去完成式）sb. would/should do（希望将来用过去将来）2. would rather后的从句要用虚拟语气。
时间从句虚拟现在 were, did (动词一般过去式)虚拟过去 had done虚拟将来 did (动词一般过去式)例：I would rather I hadn’t said such unkind things to you. （虚拟过去）I'd rather you came here for the answer tomorrow morning. （虚拟将来）I’d rather you posted the letter right away. (虚拟现在)3. suggest+（that）S+should+do…表示愿望、建议、请求等主观意向的动词之后的宾语从句，谓语用should ＋动词原形，should 常常省略。
这类词有：decide，demand，desire，insist，order，propose，suggest，recommend，requested， require 等。
注意：1. suggest 当“建议”讲时，其宾语从句用虚拟语气；当“暗示、表明”时，用陈述语气2. insist 当坚持“看法或建议”时，宾语从句用虚拟语气；当坚持“某个事实”时，用陈述语气。
判断改错：（错） Your pale face suggests that you（should）be ill.（对） Your pale face suggests that you are ill.（错） I insisted that you（should）be wrong.（对） I insisted that you were wrong.III. 虚拟语气用在主语从句中It is demanded / necessary / a pity + that…等结构的主语从句，谓语动词用should 加动词原形，should 可省略。
It is 可用的词有三类 that （should）dosuggested, ordered, required, proposed, demanded, requested, insisted等important, necessary, natural, imperative, strange等a pity, a shame, no wonder等IV．虚拟语气用在同位语从句中。
某些表示建议、请求、命令等主观意向的名词后同位语从句需用虚拟语气，其表达形式为(should) ＋动词原形。
这类名词常见的有：advice，suggestion，proposal（提议），order， demand，desire，request，requirement，recommendation（推荐），plan，resolution（决议）， idea等。
eg. We are all for your proposal that the discussion ( should )be put off．V．虚拟语气用在表语从句中。
某些表示建议、请求、命令等主观意向的名词作主语时，表语从句需用虚拟语气，其表达形式为(should) ＋动词原形。
这类名词常见的有：advice，suggestion，proposal，order， demand，desire，request，requirement，recommendation以及plan，idea，resolution等。
eg. My suggestion is that the mayor (should)present the prizes.VI．虚拟语气用在定语从句中It is（about ／high）time ＋that sb.did sth/should do sth..eg. Don't you think it's about time we went home？注：在this is the first time ／second time that．．．句型中，从句中谓语动词用陈述语气完成时态。
eg.Is this the first time that you have visited Hongkong？VII. 虚拟语气用在让步、方式、目的状语从句中1．在带有even if/ even though引导的让步状语从句的主从复合句中，主句和从句都用虚拟语气，动词形式与含有非真实条件句的虚拟语气相同。
如: Even if he had been ill, he would have gone to his office. 即使生了病，他俩去办公室。
2．由as if或as though引导的状语从句表示比较或方式时。
从句谓语形式为动词的过去式(be 用were)或“had十过去分词”。
如: He treated me as if I were a stranger. 他那样对待我，好像我是陌生人似的。
She talked about the film as if she had really seen it. 她谈论那部影片，就好像她确实看过一样。
3．虚拟语气用在lest（唯恐、免得），for fear that及in case引导的目的状语从句中。
在由lest 等引导的目的状语从句中需用虚拟语气，表示“以防，以免”等意思，其谓语动词多由should ＋动词原形构成，should也可省略。
eg. He was punished lest he should make the same mistake again．VIII．虚拟语气用情感语言中1．虚拟语气在表示客气、遗憾以及祝愿等场合中，使用虚拟语气。
eg.You shouldn't have been following him so closely；you should have kept your distance．2．If only sb./sth. +时态后退型的谓语eg. If only I had known the result of the examination.IX.虚拟语气的特殊用法：1. 省掉if的条件从句结构：Had you asked me, I would have told you.(=If you had asked me,…)2.有时虚拟条件不用条件从句而用不定式、分词、介词、名词、连接词或定语从句来表示，如：A true friend would not do such a thing.(=If he were a true friend, he would...)3. 有时条件从句中的动作和结果从句中的动作发生的时间不一致，如：If he had followed the doctor’s advice, he would be quite all right now.If I were you, I would have gone home.虚拟语气练习题：1. If you were old enough, I ________ you to go there yesterday.A. will allowB. should allowC. would have allowedD. had allowed2. The secretary suggested that they ________ the men in at once.A. had broughtB. should have broughtC. broughtD. bring3. __________I you, I would go with him to the party.A. WasB. Had beenC. Will beD. Were4. It is strange that such a thing _________ in your class.A. will happenB. happensC. should happenD. happened5. How I wish I ________ to repair the watch! I only made it worse.A. had triedB. hadn't triedC. have triedD. didn't try6. If he _______ to the teacher attentively, he _______ the answer to the problem now. A. had lis tened, would have known B. listened, would knowC. listened, would have knownD. had listened, would know7. I was busy yesterday, otherwise I _______ your birthday party.A. attendedB. had attendedC. would attendD. would have attended8. If only I _________ how to operate an electronic computer as you do.A. had knownB. would knowC. should knowD. knew9. The two strangers talks as if they _______ friends for years.A. wereB. would beC. have beenD. had been10. It is high time we _______ up our results.A. sumB. summedC. will sumD. would sum11 The librarian insists that John _______ no more books from the library before he returns all the books he had borrowed.A. will takeB. tookC. takeD. takes12. But for the guidance of our instructor(导师) , we _______ in the experiment.A. shouldn’t succeedB. could not have succeededC. will not succeedD. should not have succeeded13. It’s about time people______ notice of what women did during the war.A. takeB. tookC. have takenD. will take14. She couldn't have answered the question if she ________ a few books on worldhistory.A. hadn’t readB. hasn’t readC. wouldn’t readD. didn’t read15. Isn’t it about time that you ________ to pick up the visitors from New York?A. had goneB. should goC. goD. will go16. The young man insisted that he ________ nothing wrong and ______ free immediately.A. did; setB. had done; should be setC. do; be setD. had done; must be set17. Your advice that______ till next week is reasonable.A. she waitsB. she waitC. wait sheD. she waited18. It was essential that we_________ lease（条约、合同） before the endof the month.A. signB. signedC. had signedD. were signing19. I wish that I ______ with you last night.A. wentB. have goneC. could goD. could have gone20. He speaks Chinese so fluently as if he ______a Chinese.A. wereB. had beenC. isD. has been21. Looking round the town, he felt as though he away for ages.A. has beenB. wasC. isD. had been。