虚拟语气在英语文法中有三种语气，即直述式语气(In dicative Mood)、祈使语气(Imperative Mood)和虚拟语气(Subjective Mood)，其中前两种我们早已熟悉了，这里则不多谈了，女口：How beautiful she is!则是直述式语气，而Hurry up! Do n't hurry up则是祈使语气。
我们主要来看看虚拟语气的主要用法。
虚拟语气主要是用来表达一种无法实现的愿望，一种与事实相反的情况，或者将不可能实现的，或可能性很小的事实，假想为事实予以表述。
这样的动词结构称为虚拟语气。
它主要有三种形式，即与现在事实相反的假设，与过去事实相反的假设，与将来事实相反的假设。
它们具体结构如表8 —7。
虚拟语气的构成虚拟语气其他习惯用法简表1语法辨析In correct: If I was a girl, I would marry youCorrect: If I were a girl, I would marry you表示与现在事实相反的虚拟语气时，if条件句中的be动词一律用were，这句话应译为我要是个女孩，我就嫁给你。
实际上不可能是个女孩。
In correct: If I were you I will not worryCorrect: If I were you I should n't worry现在时的虚拟语气主句要用should或would加动词原形，这句话应译为我要是你的话，就没有必要烦恼。
要注意这种语态用在这里实际上是想把要讲出的观点表达得婉转些，有礼貌些。
In correct: God forgives you!Correct: God forgive you!这里的主语God是第三人称单数，之所以动词不加s是因为要表达一种祝愿，即人力所不能及的事情，实际上是forgive前有一助动词should, May 等,但在口语中将其省略了。
如：May you be happy祝你幸福。
In correct: If the weather was nice yesterday,we would have gone to the zooCorrect: If the weather had been nice yesterday we would have gone to the zoo因句中有 yesterday 一词即表示的是与过去相反的事实，即昨天天气很不好， 我们也未去动物园，所以if 条件句应用had+过去分词。
Incorrect: If it is was not snowing right now,I will go for a walkCorrect: If it was (were) not snowing right now ， I would go for a walk虚拟语态be 动词作助动词时，则可用 was 来取代were,女口 was to 。
虚拟语 态中的动词如果是表示正在进行之中也要用进行时态。
Incorrect: If you had taken my advice, you would have been better now Correct: If you had taken my advice, you would be better now这句话的意思是如果你以前要是能听我的忠告的话， 你现在就会好多了。
其条 件句是与过去事实相反的虚拟句， 而主句是与现在事实相反的虚拟句， 这在语法 书中叫做混合虚拟条件句。
例如： If I had caught that plane ， I would be dead now 即： The plane I intended to catch crashed and everyone was killedhe would go home at once he would go home at once在虚拟条件句中的if 可以省略，但if 省略后其句子的结构要采用倒装语序 Incorrect: Supposing your teacher saw you with me What does she think? Correct: Supposing your teacher saw you with me ， what might she think?这句话中没有if 条件句，但仍要用作虚拟语态。
这里因为有些分词或介词短 语，起到了从句的作用。
这些短语有： without ， providing, supposing ， but for(you) … Incorrect: To see the girl ， you will like her Correct: To see the gir ，l you would like her这里的条件句是用不定式取代了。
Incorrect: I'm sorry I did have come here by car Correct: I'm sorry I should have come here bycar 这里的条件句被省略了， 其意为我真应该坐小车来。
同样在句意不会混淆的情 况下，主句也有时可以被省略，女口： What if we should fail!(我们万一失败了如何)。
If he could do it, why not? (如果他能做，他怎么会不干呢 ?)Incorrect: If the earth were (was) to turn from east to wes ，t I will give you this car as a giftCorrect: If the earth were(was) to turn from east to west I would give you this car as a gift条件句中也常用 were to 来表示说话者认为可能性极小或根本不可能的事。
In correct: If you'd have told him early , he would have passed the examCorrect: If you had told him early , he would have passed the exam非正式口语中往往听见外国人讲：'d have+ pp （过去分词）但仍没有人认为它是 正确的句子，不易为我们效仿。
Incorrect: He were you ， he would go home at onceCorrect: Were he you ， Correct: If he wereyou ，In correct: The little girl looked as if she would have see na ghostCorrect: The little girl looked as if she had see n a ghost要注意的是as if从句中如果用虚拟语气，它的用法要与if条件句的动词结构相同，即与现在事实相反动词用过去式，be动词用were,而与过去事实相反的动词用had+ pp （过去分词）。
另外更要注意的是，并非所有as if从句都要用虚拟语气。
如：Itlooks as if it is going to snow （看天好像要下雪）即是真实条件句。
In correct: I should have come here early but I had bee nbusyCorrect: I should have come here early but I wasbusybut是转折连词，其后的句子是真实句，而不是虚拟句。
In correct: To tell the truth，I wish I know her address nowCorrect: To tell the truth, I wish I knew heraddress nowwish的宾语从句中要用虚拟结构，与现在事实相反的条件动词要用过去式，be动词用were,与过去事实相反的条件动词要用had+过去分词。
女口：I wished I had passed that examIn correct: His homework was writte n badlyI wish he will do it better tomorrowCorrect: His homework was writte n badlyI wish he would do it better tomorrowwish要用来表示对现状不满，希望将来有所改进，则要用would加动词原形。
并非wish不能表达真正的祝愿，但是不能接从句，而要用双宾语，或不定式，如：I wish you luck （双宾语）I wish you to be a good stude ntI wish to see her at onceIn correct: I wish it will not be ano ther failureCorrect: I hope it will not be ano ther failureCorrect: I wish it would n ot be ano ther failure要注意hope与wish的不同用法。
2例题解析［例1］If he ___ on tourists for his bus in ess he would have to close his shopA dependsB will dependC depended Dhas depended［答案］C. 这是与现在事实相反的假设。
应译为：如果他仅靠旅游来做生意的话，他早就要关门了。
［例2］Had she been younge, she ___ more beautifulA had beenB might have beenC might beD would be［答案］B. 因其条件句是省去if的与过去事实相反的假设。
［例3］If you ____ that TV play last ni ght，you would n't be sleepyA have n't watchedB did n't watchC had n't watchedD would n't have watched［答案］C. 因是与过去事实相反的假设。