虚拟语气

陈述语气：简单而言就是描述事实。

The rabbit ate the carrot.

一种比较特殊的陈述语气，称为条件语气：

If I see the rabbit tomorrow, I will bite him.

起始语气：暗含命令/请求。

结构：用第二人称（你）和一般现在时，然后将第二人称去掉并保持动词原形。

Rabbit, eat the carrot!

虚拟语气用法

表示不可能的假设

• 表示和现在事实相反

结构：条件句用过去式，主句用 would + 动词原形。

If I saw the rabbit now, I would bite him.

• 表示将来时间里，可能性很小的动作（与将来相反）

结构：条件句 should + 动词原形，主句 would + 动词原形。

If I should see the rabbit tomorrow, I would bite him.

• 表示与过去已经发送的事实相反

结构：条件句 had + 动词的过去分词，主句 would have + 动词的过去分词。

If I had seen the rabbit a few days ago, I would have bitten him.

表达愿望、请求、建议、命令等

wish（表示希望比较小的事情发生，而类似的 hope 则是比较中性的）

• 对现在的愿望

I wish that I were a rabbit.

I would rather that you did not eat the carrot. # 我宁愿你不会吃那胡萝卜

• 对过去的愿望

I wish that I had eaten the carrot. # 我希望我吃了那胡萝卜

I would rather that you had not eaten the carrot. # 我宁愿你没吃掉那胡萝卜

• 对将来的原因

I wish that I could eat the carrot.

与 wish 类似的词还有 demand、suggest、insist、order 等，其后面接的虚拟语气都是 should + 动词原形。

I demand that you should give me a carrot. # 我要求你给我一根胡萝卜

I demanded that you should give me a carrot. # 我过去要求你给我一根胡萝卜