在英语中，随着说话人意图的不同，动词需用不同的形式，称为语气。虚拟语气是三种语气中的一种。它既可以表达与事实相反的陈述或某种愿望与空想，也可以表达建议，要求，请求与命令等语气。虚拟语气是通过动词的时态与时间的不一致来体现的。虚拟语气主要有以下两类：
一、与事实相反的陈述或某种愿望与空想
它的表现形式为：
1、条件句中的虚拟语气
1）由if 引导的条件句，有可能是直陈语气，也有可能是虚拟语气。可根据以下两条来判断具体的语气。
a)根据含义。如果是纯粹假设的情况或是发生的可能性不大的情况，则是虚拟语气。如：
If I were you , I would reconsider their proposal .
If I had left a little earlier , I would have caught the train.
b)根据时态与时间的矛盾。如果时间是将来，但是时态却是过去时，则是虚拟语气。 如：
(1)If it________tomorrow, I would stay at home.
(2)If it________tomorrow, I will stay at home.
A. rain B. rainedC. rainsD. will rain
分析：在(1) 句中，主句的时态与时间不一致，所以判断是虚拟语气，答案是B。
在(2) 句中，主句的时态与时间一致，所以判断是直陈语气，再根据在条件状语从句中，要用一般现在时表达将来时间，所以答案为C。
2)条件句中的虚拟语气有以下三类：
a)与现在事实相反，谓语动词如下：
从句：过去时
主句：would / should / could / might +动词原形。如：If I were you , I would ask our teacher for advice.
b)与过去事实相反，谓语动词如下：
从句：过去完成时
主句：would / should / could / might have +过去分词。如：
If I hadn’t taken the wrong bus , I wouldn’t have missed the contest.
c)与将来事实相反，谓语动词如下：
从句：过去时 / should + 动词原形 / were to + 动词原形
主句：would / should / could /might + 动词原形
If I had enough money next month, I would buy the dictionary.
3)如果条件从句中包含有should, 动词be 或 have， 可把if省略,并把should,动词be或have 放在主语前面。 如：
Had we made preparations , we might have succeeded.
Should there be a flood , what should we do ?
2、Wish 引导的宾语从句 ，根据时间的不同，可分为以下三种；
1）与现在事实相反，从句动词用过去时。如
I wish I were as healthy as my cousin.
2）与过去事实相反，谓语动词用过去完成时。如：
We wish we had paid more attention to our pronunciation.
3)与将来事实相反，谓语动词用would / could +动词原形。如：
I wish I would try again.
3、as if 引导的从句。如：
They talked as if they had been friends for years.
It seems as if it were spring already.
4、以in order that, so that 引导的目的状语从句。如：
The professor spoke slowly in order that the listeners could hear him clearly.
5、以 It is time 以及 would rather 引导的从句，从句中的动词都用过去时。如：
It is time we stopped this practice
I would rather you came tomorrow.
二、虚拟语气还可用来表示愿望，建议，命令等
1、在suggest , order , demand , ask , command，propose , request, insist 等表示建议,要求,请求,命令的动词引导的宾语从句中，谓语动词为：(should) +动词原形。如：
We suggested that they (should ) make a trip to Hongkong next year.
She insisted that we (should )take up the matter at the meeting.
2、在suggestion, propsal , order , plan 等引导的表语从句和同位语从句中，谓语动词为(should )+ 动词原形。如：
My suggestion is that we (should )send a few comrades to help the other groups.
My idea is that we (should )challenge the other groups to a friendly competition.
3、在 it is desired, it is suggested, it is requested, it was ordered, it was proposed. it is necessary, it is important, it has been decided等结构后的主语从句中，谓语动词为 ：(should) +动词原形。如：
It is necessary that he (should ) be sent there at once.
It is desired that we (should )get everything ready by tonight.
4、在 it is a pity, it is a shame, it is incredible, it is strange, it is no wonder等结构后的主语从句中， 谓语动词为：should +动词原形，以表示惊奇，怀疑，不满 等情绪。如：
It is a great pity that he should be so conceited.
It is strange that she should have failed to see her own shortcomings.
(作者单位系甘肃省白银公司第一中学)