虚拟语气表示说话人所说的话是一种强烈的主观愿望､假设､猜测､建议､可能或空想,因此虚拟语气常用在含有非真实条件从句的复合句中｡虚拟语气中,主句与从句中谓语动词的形式如下:
　　


　　
　　If he were here now, I could ask him the question. 如果他现在在这儿,我可以问他这个问题｡(与现在事实相反)
　　If they had arrived earlier, they could have met him. 如果他们早一点儿到达,他们就会见到他了｡(与过去事实相反)
　　If the sun were to rise in the west, I would marry you. 如果太阳从西边出来,我就会嫁给你｡(将来实现的可能性很小)
　　If it should snow tomorrow, we would put off our trip. 如果明天下雪,我们将会推迟旅行｡(将来实现的可能性很少)
　　注意:
　　1. 当从句谓语动词用过去式时,无论主语是什么人称, be 动词的过去式一般用 were｡
　　2. 主句谓语动词中的 would 可根据情况由 should(用于第一人称), could 或 might替换｡
　　3. 可以省去虚拟条件从句中的连词if,而将 were,had 或 should 提至句首｡例如:
　　Should it rain tomorrow, I would not go to Beijing. 万一明天下雨,我就不去北京｡
　　4. 虚拟语气的主句与从句的谓语动词形式原则上应前后呼应｡但如果主句与从句的谓语动词所表示的动作发生的时间不一致,谓语动词形式应根据各自所体现的时间关系加以适当的调整｡例如:
　　If he had told me his telephone number yesterday, I could phone him now. 如果昨天他告诉我他的电话号码,现在我就可以给他打电话了｡
　　5. 有时假设的情况并不用条件状语从句,而是用介词短语来表示｡例如:
　　Without electricity(=If there were no electricity), human life would be quite different today. 如果没有电的话,人类今天的生活就完全不同了｡