英语的动词有三种语气形式，即陈述语气、祈使语气和虚拟语气。陈述语气用来说明事实或就事实提出询问，可用于陈述句、疑问句和某些感叹句中;祈使语气用于表示请求、命令、建议或警告等。　　虚拟语气是谓语动词的一种特殊形式，用来表达假设、主观愿望、猜测、建议、可能或空想等非真实情况。如：　　He is honest. 他很诚实。 (陈述语气)　　Don‘t be late next time. 下次别迟到。 (祈使语气)　　If I were you ，I would not go. 我要是你，我就不会去。 (虚拟语气)　　I wish I had a lot of money. 要是我有很多很多钱就好了。 (虚拟语气)　　编辑本段第一类　　虚拟语气在条件句中的用法：　　条件句有真实条件句和虚拟条件句两种。真实条件句所表示的假设是有可能发生的，此时主句不用虚拟语气;而虚拟条件句则表示一种假想，与事实相反或不大可能会发生，此时用虚拟语气。如：　　If I have time，I will go. 假若我有时间，我就去。 (陈述语气) If I were you，I would go. 假若我是你，我就去。 (虚拟语气 )　　时态类型主句谓语形式条件句的谓语形式例句

　　与现在事实相反would/should/could/might+ V原动词过去式 did

　　*be 多用were　1. If I were you, I should study English.

　　2. I would certainly go if I had time.

　　与过去事实相反would/should/could/might + have done动词过去完成式

　　had done1. If you had taken my advice, you would not have failed in the test.

　　2. If I had left a little earlier, I would have caught the train.

　　与将来事实相反would/should/could/might + V原①动词过去式

　　②should +V原

　　③were + to do　1.If you came tomorrow, we would have the meeting. ①

　　2. If it were to rain tomorrow, the meeting would be put off.③

　　*规律总结：从句都往过去推一个时态，如：与现在相反的if从句就用过去时;与过去相反用过去完成时(即过去的过去)​​​

　　注：特别说明　　1、l would/should/could/might主句谓语中的should主要用于第一人称后;would表示结果还表示过去经常常常做某事，might表示可能性，could表示能力、允许或可能性。比较：　　If you tried again ，you would succeed. 要是你再试一试，你就会成功的。 (would表结果)　　If you tried again， you might succeed. 要是你再试一试，你可能会成功的。 (might表可能)　　If you tried again ，you could succeed. 要是你再试一试，你就能成功了。(could表能力)　　2、错综时间虚拟条件句 即条件从句与主句所指时间不一致，如从句指过去，而主句即指的是现在或将来，此时应根据具体的语境情况，结合上面提到的三种基本类型对时态作相应的调整：　　If it had rained last night, the ground would be wet now. 要是昨晚下过雨的话，现在地面就会是湿的。　　You would be much better now if you had taken my advice. 假若你当时听我的话，你现在就会好多了。　　3、If虚拟条件句的否定(含蓄条件句) 常考两个句型：If it weren’t for…和If it hadn’t been for…，其意为“若不是(有)” “要不是”。如：　　If it weren’t for water, no plant could grow. 要是没有水植物就无法生长。　　If it hadn’t been for your assistance ，we wouldn’t have succeeded.　　=But for your assistance ，we wouldn’t have succeeded.　　=Without your assistance ，we wouldn’t have succeeded.如果没有你的帮助，我们不会成功的。　　4、If虚拟条件句的倒装形式，即把were, had, should置于句首。例：　　Were I in school again (= If I were in school again), I would work harder.如果我能再上一次学，我会学习得更努力。　　Had you asked me, I would have told you. (=If you had asked me,…)如果你问我，我会告诉你。编辑本段第二类　　使用虚拟语气的常见结构或从句：　　1.*wish与hope接宾语从句的区别在于：hope表示一般可以实现的希望，宾语从句用陈述语气。wish表示很难或不大可能实现的希望,宾语从句用虚拟语气。试比较：　　(1) We hope they will come. (We don’t know if they can come.)　　(2) We wish they could come. (We know they are not coming.)我们希望他们能来。　　2.if only 与 I wish一样，也用于表示与事实相反的愿望，其后所虚拟语气的时态与 wish后所接时态的情况相同：　　If only she had had more courage! 她再勇敢一些就好了。　　If only I had listened to my parents! 我要是当时听了父母的话就好了。　　If only she would go with me! 她要是愿意和我一道去就好了!　　*if only 通常独立使用，没有主句。　　3.l would rather后句子用虚拟语气 只分现在和过去　　在would rather, would sooner, would just as soon后的that从句中, 句子谓语习惯上要用虚拟语气， 表示"宁愿做什么" ，具体用法为：　　①　一般过去时表示现在或将来的愿望　　I’d rather you went tomorrow (now). 我宁愿你明天(现在)去。　　②　用过去完成时表过去的愿望　　I’d rather you hadn’t said it. 我真希望你没有这样说过。　　4.l as if (though)从句用虚拟语气　　以as if (as though)引导的方式状语从句或表语从句，有时用虚拟语气,则与wish用法相同，例：　　He acts as if he knew me. 他显得认识我似的。　　They treat me as though I were a stranger. 他们待我如陌生人。　　He talks as if he had been abroad. 他说起话来好像曾经出过国。　　注：两点说明　　(1) 从句所表示的内容若为事实或可能为事实，也可用陈述语气：　　It looks as if we’ll be late. 我们似乎要迟到了。　　(2) 注意 It isn’t as if…的翻译：　　It isn’t as if he were poor. 他不像穷的样子(或他又不穷)。编辑本段第三类　　从句中should+动词原形，should可省略　　1. 在 lest ，for fear that( 以免) ,in case(以防)引导的目的状语从句中的虚拟语气　　She walked quietly lest she (should)wake up her roommates. 她走得很轻以免吵醒她的室友。　　2. 表应当做 值得做 一类动词后的宾语从句　　建议advise, suggest, propose, recommend命令order, command　　请求ask, demand, require, request指示direct　　敦促urge提议move, vote　　希望desire坚持insist　　打算intend安排arrange　　例如：　　I insisted that he (should)stay. 我坚持要他留下。　　He urged that they go to Europe. 他敦促他们到欧洲去。　　He suggested that we shouldleave early. 他建议我们早点动身。　　He ordered that it (should)be sent back. 他命令把它送回去。　　I ask that he leave. 我要求他走开。　　He requires that I (should)appear. 他要求我出场。　　I move that we accept the proposal. 我提议通过这项提案。　　He arranged that I should go abroad. 他安排我去国外。　　She desires that he do it. 她希望他做此事。　　The general directed that the prisoners should be set free. 将军指示释放那些俘虏。　　*suggest表“暗示”insist表“坚持认为”不用虚拟语气　　比较：　　He insisted that Ihad read his letter. 他坚持说我看过他的信。　　He insisted that I should read his letter. 他坚持要我看他的信。　　He suggested that we (should) stay for dinner. 他建议我们留下吃饭。　　I suggested that you had a secret understanding with him. 我觉得你与他心照不宣。　　3. order,suggestion,idea,plan, proposal, advice, demand等名词后的表语从句或同位语从句　　Our suggestion is that you( should)be the first to go. 我们的建议是你应该第一个去。　　4.*advice, agreement, command, decision, decree, demand, determination, indication, insistence, order, preference, proposal, request, requirement, stipulation, suggestion, idea, plan, order　　l “It is (was)+ 紧急 重要-- 带感情色彩　　上述demand/suggest等动词过去分词 或　　important,natural,strange ,necessary，surprised, appropriate等形容词 后的主语从句　　1. It is ordered that the army (should) get there by 4 a.m.　　2. It is necessary that she (should) be sent there at once.　　注：*It is necessary，important，strange，natural， advisable, anxious, compulsory, crucial, desirable, eager, essential, fitting, imperative(绝对必要), impossible, improper, obligatory, possible, preferable, probable, recommended, urgent, vital etc. ;it is a pity;It is requested/suggested/desired/proposed　　编辑本段第四类　　It’s time后的从句用虚拟语气　　从句谓语通常用过去式表示 (早)该干某事了　　*有时也用过去进行时或“should+动词原形”(较少见，且should不能省略)　　ex. It’s time we went [were going, should go]. 我们该走了。　　It’s time I was in bed. 我该上床睡了。(不用were)　　It's time = It is (the very/high/right/about) time编辑本段wish和as if引导的虚拟1.表示与现在事实相反的愿望

　　构成：主语 + wish (that) + 从句主语 + 动词过去式 (be 一律用were)　　例如：I wish I knew everything in the world.我希望我知道世界上所有的事。　　I wish that the experiment were a success.我希望这个实验是成功的。　　We wish we had wings.我们希望有翅膀。

　　2.表示与过去事实相反的愿望

　　构成：主语 + wish (that) + 从句主语 + would/could + have + 过去分词或had + 过去分词　　例如：I wish that you had called yesterday.我希望你昨天来过。　　I wish that I could have gone with you last night.我希望我昨晚能和你一起去。　　I didn’t go to the party, but I do wish I had been there.我没有去参加晚会，但是我真的希望我去过那里。

　　3.表示将来不大可能实现的愿望

　　构成：主语 + wish (that) + 从句主语 + would/should/could/might + 原形动词　　例如：I wish that he could try again.我希望他能再次尝试。　　I wish that someday I should live on the moon.　　We wish that they would come soon.　　II. AS IF 引出的虚拟。　　As if….表好像……我们经常会利用一下句型来表达不能实现的虚拟状态：It is as if……。 (就好象是……)　　As if + 从句， 主句。 (好像…… Sb.+ do…)表达一种假设的条件。而 As if 之后的假设内容的语法结构和wish虚拟的结构一样。　　L. 33 A Day to Remember 中原句， “As if this were not enough to reduce you to tears, your husband arrives.” 就利用了和现在事实相反的假设虚拟。北京新东方名师指出，要善于总结出一些学习语法的技巧，如利用对比，举例等方法进行学习。　　注：Something is to happened，I'm to face it。编辑本段注意事项：　　使用虚拟条件句时要注意的几点：　　1.当条件状语从句表示的行为和主句表示的行为所发生的时间不一致时，被称为“错综时间条件句”，动词的形式要根据它所表示的时间作出相应的调整。如：　　If you had followed my advice just now, you would be better now.　　If you had studied hard before, you would be a college student now, and you would graduate from a college in four years’ time.　　2.if 省略句　　在条件句中可省略if, 把were, had, should提到句首 , 变为倒装句式。如：　　If I were at school again, I would study harder.　　→ Were I at school again, I would study harder.　　If you had come earlier, you would catch the bus.　　→ Had you come earlier, you would catch the bus.　　If it should rain tomorrow, we would not go climbing.　　→ Should it rain tomorrow, we would not go climbing.　　注意：若省略的条件句中的谓语动词是否定形式时，不能用动词的缩略形式。如：我们可以说：Were it not for the expense, I would go abroad now. 但不能说：Weren't it for the expense, I would go abroad now.　　3.用介词短语代替条件状语从句。常用的介词有with, without, but for。如：　　What would you do with a million dollars? ( = if you had a million dollars)　　We couldn't have finished the work ahead of time without your help. ( = if we hadn't got your help)　　But for the rain ( = If it hadn't been for the rain ), we would have finished the work.　　4.含蓄条件句　　有时为了表达的需要，在虚拟语气中并不总是出现if引导的条件句，而通过其他手段来代替条件句。　　I was ill that day. Otherwise, I would have taken part in the sports meet. (副词)　　He telephoned to inform me of your birthday, or I would have known nothing about it. (连词)　　A man who stopped drinking water would be dead in about seven days. (定语从句)　　I might have given you more help, but I was too busy. (连词)　　Everything taken into consideration, they would have raiser their output quickly. (独立主格结构)　　混合型与含蓄型虚拟语气　　1。混合型虚拟语气：　　当虚拟条件从句与结果主语所表达的时间不一致时，被称为“混合条件句”，这种虚拟语气被称为“混合型虚拟语气”，动词的形式要根据它所表达的时间作相应调整。如：　　If you had followedthe doctor's advice ,he would be all right now.(条件从句表达的时间是过去，因此用had+过去分词;主句表示的时间是现在，因此用would+动词原形)　　2.含蓄型虚拟语气：　　有时候，虚拟条件不是通过if引导的条件句来表示，而是暗含在上下文中　　(1).用but for 、without(如果没有)等来代替条件从句，如　　Without electricity human life would be quite different=If there were no electricity ,human life would be quite different　　(2) 用otherwise、or(or else),even though等表示与上文的情况相反，从而引出虚拟语气。如：　　I lost your address.Otherwise,I would have visited you long before. =I lost your address.If I hadn't lost your address ,I would have visited you long before.　　(3) 虚拟条件通过but暗示出来。如：　　He would have given you more help,but he was too busy　　他本来会给你更多的帮助，但是他太忙了。也就是说，如果那时他不忙，他可以给你更多的帮助。句中but he was too busy实际上暗示了一个虚拟条件——如果那时他不忙　　He would lose weight,but he eats too much　　他本来可以减肥的，但是他吃的太多了。也就是说，如果他吃得不多的话，他是可以减肥的。句中的but he eats too much实际上暗示了一个虚拟条件——如果他吃得不多。