1. 虚拟语气用于条件状语从句

注意:主句中的should通常用于第一人称,would可用于任何人称,同时也可根据意思用情态动词could, might等代替should, would。

1)表示与现在事实相反:

If I were you, I should stay at home.

If the peasants could farm the land themselves, food production would be much higher.

If fewer cash crops were grown, more food could be produced and there would be less or no starvation.

2)表示与过去事实相反:

If you had come yesterday, you would have met him.

If the hurricane had happened during the daytime, there would have been many deaths.

3)表示与将来事实相反:If you came tomorrow, we would have the meeting.

If it were to/should rain tomorrow, the meeting would be put off.

If it should rain, the crops would be saved.

4)当条件状语从句表示的行为和主句表示的行为所发生的时间不一致时,动词的形式要根据它所表示的时间来调整。例如:If you had followed the doctor's advice, you would be quite all right now. (从句说的是过去,主句指的是现在.)

5)以上句型可以转换成下列形式:①从句省略if,用倒装句式"were, had, should+主语"。例如:Were I in school again, I would work harder. Had you been here earlier, you would have seen him. Should there be a meeting tomorrow, I would come.②用介词短语代替条件状语从句。例如:Without air, there would be no living things. I would not have succeeded but for your help.

2.虚拟语气用于宾语从句

1)"wish+宾语从句"表示不能实现的愿望,汉语可译为"可惜……"、"……就好了"、"悔不该……"、"但愿……"等。表示现在不能实现的愿望,从句的谓语动词用过去式;表示将来不能实现的愿望,用"would(could)+动词原形";表示过去不能实现的愿望,用"had+过去分词"或"(could)would + have + 过去分词"。例如:

I wish we could go to the seaside today.

I wish you told me earlier.

We wish we had arrived there two hours earlier.

2)虚拟语气在动词arrange, command, demand, desire, insist, order, propose, request, require, suggest 等后面的宾语从句中,用"(should)+动词原形"。例如:

I suggested that the meeting (should) be put off.

The doctor ordered that she (should) stay in bed for a few days.

They demanded that the black people should be treated as well as white people.

注意:insist作"力言"、"强调"解时,宾语从句不用虚拟语气。只有当insist作"坚持(应该)"解时,宾语从句才用虚拟语气。例如:

Mike insisted that he had never stolen anything.

I insisted that you give me my money back.

3.虚拟语气用于表语从句、同位语从句做advice, idea, order, demand, plan, proposal, suggestion, request 等名词的表语从句和同位语从句,其谓语动词要用虚拟语气的结构"(should)+动词原形"。例如:

We all agreed to his suggestion that we (should)go to Beijing for sightseeing.

My idea is that he (should) do exercises first.

4.虚拟语气用于以as if(as though)引导的表语从句或状语从句

如果从句表示与现在事实相反,谓语动词用一般过去时;表示与过去事实相反,谓语动词用"had+过去分词";表示与将来事实相反,谓语动词用"would(might, could )+动词原形"。例如:

He looked at me as if I were mad.

He speaks English so fluently as if he had studied English in England.

It looks as if it might rain.

但as if(as though)后的从句也常用陈述语气,这是因为从句中的情况往往是可能发生的或可能被设想为真实的。例如:

It looks as if our side is going to win.

5.虚拟语气用于主语从句

在主语从句中,谓语动词的虚拟语气结构用"should+动词原形"的结构,表示惊奇、不相信、惋惜、理应如此等。例如:

It is necessary (important, natural, desirable, advisable, strange, etc.) that we should clean the room every day.

It was a pity (a shame, no wonder, etc.) that you should be so careless.

It will be desired (suggested, decided, ordered, requested, proposed, etc.) that she should finish her homework this afternoon.

在上述三种主语从句中,should意为"应该"、"竟然",可以省去,但不可换用would。主句所用动词的时态不限。

注意:这种从句表示的是事实。如果说话人对这种事实表示惊奇,就可用虚拟语气。反之,如果不表示惊奇,that从句也可用陈述语气。例如:

It is strange that he did not come yesterday.

It is a pity that you can't swim.