英语的动词一般有三种不同的语气：陈述语气、祈使语气和虚拟语气。虚拟语气表示说话人所说的不是事实，而是一种假设、愿望、怀疑或推测，它主要用于if条件状语从句，也可用于主语从句、表语从句、宾语从句和同位语从句等。

　　一、虚拟语气在条件句中的应用

　　1．对现在情况的虚拟

　　对现在的情况进行虚拟时，非真实条件状语从句的谓语动词用一般过去时，主句谓语动词使用"should/would/could/might＋动词原形"的形式。

　　We would go with you if we had time now.

　　如果我们现在有时间，就和你一起去。

　　If he were you, he should try his best to go to college.

　　如果他是你，他会尽其所能去上大学。

　　[即时演练1]　用所给词的适当形式填空

　　①(湖南高考改编)Sorry, I am too busy now. If I had (have) time, I would certainly go for an outing with you.

　　②If you were (be) a big boss, you could/might understand how hard a period I am in.

　　2．对将来情况的虚拟

　　对将来的情况进行虚拟时，非真实条件状语从句用"should＋动词原形"，或"were to＋动词原形"，或"动词过去式"的谓语动词形式，主句使用"should/would/could/might＋动词原形"的谓语动词形式。

　　If it should rain this afternoon, the basketball matchcould be put off.

　　要是今天下午下雨，篮球比赛就延期举行。

　　If it were to be sunny tomorrow, we would go out for a picnic.

　　如果明天天气晴朗，我们会出去野餐。

　　If he camehere tomorrow, he might get the chance.

　　他若是明天能来，就能得到这个机会。

　　[即时演练2]　用所给词的适当形式填空

　　①(安徽高考改编)Grace doesn't want to move to New York because she thinks if she were_to (be) live there, she wouldn't be able to see her parents very often.

　　②If it rained (rain) tomorrow, we wouldn't go hiking.

　　③-Why do we get up so early?

　　-If we should_miss (miss) the flight we would have to stay here for another day.

　　3．虚拟语气的省略

从句中有should, were 等助动词时，可以把if省略，并将助动词提至句首，从而构成