1、虚拟语气用于条件状语从句中

(1)表示与现在事实相反的假设，条件状语从句中的谓语动词用“过去式(be动词的过去式用were)”，而主句中的谓语动词用“would / should/ could / might + 动词原形”。如：

If I were a boy, I would join the army.

If the had time, she should go with you.

(2)表示与过去的事实相反，条件状语从句中的谓语动词用过去完成时，主句中的谓语动词则用“would / should / might / could + have +过去分词”。如：

If he had taken my advice, he would have succeeded in the competition.

(3)表示与将来事实相反，条件状语从句中的谓语动词一般过去时或should(were to) + 动词原形，而主句中的谓语动词则用would / should/could might + 动词原形。如：

If it were to rain tomorrow, the football match would be put off.

(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作相应调整。如：

If they had worked hard, they would be very tired.(从句说的是过去，主句指的是现在)

以下表格是虚拟语气用于条件状语从句中时，主句和从句谓语动词的形式：

　 条件状语从句　 主句　 与过去事实相反　 had + 过去分词 should /would/could/might + have + 过去分词　 与现在事实相反　 一般过去时(be用were) would/should/could/might + 动词原形　 与将来事实相反　

一般过去时或should(were to) + 动词原形

Would/should/cold/might + 动词原形

有时侯在使用时可省略if，句子则可换成下列形式，即“were / had / should +主语”。如：

Were I a boy, I would join the army.

Had he taken my advice, he would have succeeded.

Were it not for the expense, I would go to Britain.

It is high time I went home now. = It is high time I should go home now.

●表语从句、同位语从句中的虚拟语气

在suggestion， proposal， order， plan， idea， advice， decision等需要有内涵的名词后面的表语从句、同位语从句中，要使用虚拟语气。其谓语动词应用：should+原形动词。另外连接从句的that不能省略。

例：My suggestion is that weshould go there at once.

What do you think of his proposal that we should put on a play at the English evening

用于该结构中的过去分词是表示“建议、请求、命令”等词的过去分词。如：desired， suggested， requested， ordered， proposed等。

用于该句型的形容词是：necessary, good, important, right, wrong, better, natural, proper, funny, strange, surprising ．

一些名词也可以用于 在该结构中。如：a pity， no wonder．．．．

在这种结构中，从句的位于动词用过去形式表示虚拟。

I would rather you did this instead of me.

●主语从句中的虚拟语气

从句中用“should + 动词原形”构成。而且should可以省去。用于此结构的动词有：advise, direct, agree, ask, demand, decide, desire, insist, order, prefer, propose, request, suggest等。

注意：当insist表示“坚持认为”、suggest表示“表明，显示”时，不用虚拟语气。

The look on his face suggested that he was quite satisfied with what I had done for him.

He insisted that he was honest.　

wish 后面宾语从句中的虚拟语气，按“后退一步法”处理从句的谓语动词。注意：与哪个事实相反，不能以主句的时态为判断依据，而是根据从句的意义判断。

①if条件句中如有were, should, had，可以省去if，并使用倒装语序。

②在现代英语中if条件状与从句中的谓语动词如果是be其过去形式一般用were。

●宾语从句中的虚拟语气

后退一步法是指在准确地判断了该句与哪一事实相反后，按虚拟语气的后退一步法处理从句谓语动词的时态。即：在非真实条件状语从句中，谓语动词按正常情况“后退一步”。也就是：

①与过去事实相反，在从句中用过去完成时形式表示。

②与现在事实相反，在从句中用过去一般时形式表示。

③与将来事实可能相反，在从句中用过去将来时形式表示。

主句中则用情态动词would, should, could 等加一个与从句一致的动词形式。

例：If I had come her yesterday, I would have seen him.

If I were a teacher, I would be strict with my students.

If it should snow tomorrow, they couldn’t go out.

判断是真实条件句还是非真实条件句。只有在非真实条件句中才使用虚拟语气。通过句子意思，看假设的条件是否能够实现，能够实现是真实条件句，不能使用虚拟语气；假设的条件不能实现则是非真实条件句，要用虚拟语气。

判断这个假设是与哪个事实相反。通常有三种情况：①与过去事实相反。②与现在事实相反。③与将来事实可能相反。