在含有虚拟条件句的复合句中，主从句的谓语都要用虚拟语气，现将其形式列表如下：

1. 表示与现在事实相反的假设和结果。如：

If I were you, I should(would ,could, might)tell him the truth. 要是我是你，我就会告诉他真相了。（事实上我不是你）

If she had time, she would(could, might)help me. 如果她有时间，她就会帮我了。（事实上她没有时间）

2. 表示与过去事实相反的假设和结果。如：

If I had known your telephone number yesterday, I should(would, could, might)have telephoned you. 如果昨天我知道了你的电话号码，我就会给你打电话了。（事实上我昨天不知道你的电话号码。）

If you had taken my advice, you wouldn't(couldn't) have failed in the exam. 如果你听了我的建议，你就不会考试不及格。（事实上你根本没听我的。）

3. 表示与将来事实可能相反的假设和结果。如：

If it should rain, the crops would(could, might)be saved. 假如天下雨，庄稼可能就收获了。

注：在表示与将来事实可能相反的条件从句中，were to + 动词原形比较正式，常用于书面语中。If you were to go to Beijing, you would (could, might) have a chance to visit Tian An Men Square.

二、虚拟语气的其它用法

1.虚拟语气在主语从句中的用法。在"It is important (strange, natural, necessary) that..."这类句型中，that所引导的主语从句中的谓语动词常用“(should)+动词原形”结构，表示某事是“重要”，“奇怪”，“自然”，“必要”等意义。如：

It is important that every Beijinger (should) be able to speak English. 重要的是每个北京人能说英语。

It is necessary that he (should) be sent to hospital at once. 有必要马上把他送医院。

2.虚拟语气在宾语从句中的用法。

（1）在动词wish后的宾语从句中，表示与现在或过去的事实相反，或对将来的主观愿望，从句通常省略连词that。

a.表示对现在情况的虚拟：从句动词用过去式或过去进行时（be的过去式用were）表示。如：

I wish I knew the answer to the question. 我希望知道这个问题的答案。（可惜不知道。）

I wish it were spring in my hometown all the year around. 但愿我的家乡四季如春。（只是愿望，实际根本不可能实现。）

b.表示对过去情况的虚拟：从句动词用had+过去分词。如：

I wish (that) I hadn't wasted so much time. 我后悔不该浪费这么多时间。（实际上已经浪费掉了。）

He wishes (wished) he hadn't lost the chance. 他真希望没有失去机会。（事实上机会已经失去了，他感到惋惜。）

c.表示对将来的主观愿望：谓语动词形式为“would/should/could/might+动词原形”，此时要注意，主句的主语与从句的主语不能相同，因为主句的主语所期望的从句动作能否实现，取决于从句主语的态度或意愿（非动作名词除外）。如：

I wish it would stop raining. 但愿雨能停止。

I wish you would be quiet. 我希望你安静一些。

（2）在suggest（建议）, demand（要求）, order（命令）, propose（建议）, insist（坚持要做）, command（命令）, request（要求）, desire（希望）等动词后的宾语从句中，谓语动词用“(should)+动词原形”，表示建议，要求，命令等。如：

I suggest that we (should) start the meeting at once. 我建议马上开会。

The undergraduate insisted that he (should) go to work in the south. 这位即将毕业的学生坚持要到南方去工作。

注：当suggest 表示暗示，主语为something；insist 表示坚持观点时，后接的宾语从句当用真实语气。比较：

His silence suggested that he agreed with my decision. 他的沉默暗示着他赞成我的决定。

He suggested that I (should) stick to my decision. 他建议我坚持自己的决定。

He insists that doing morning exercises does good to people's health. 他坚持认为做早操对健康有益。

He insists that he (should) do morning exercises every day. 他坚持他每天都要早操。

3. 虚拟语气在表语从句中的用法。

当主语为advice, suggestion, order, proposal等词时后接表语从句，表语从句中的谓语动词常用“(should)+动词原形”结构，表示某人建议、劝告、命令等的内容。如：

My advice is that you should practise speaking English as often as possible. 我的建议是你尽可能经常地练习说英语。

The order from the commander was that the troops should set off for the front immediately. 司令官的命令是部队立即开拔去前线。

4. 特殊的虚拟语气结构。

（1）虚拟语气用在状语从句中由as if 或as though引导的状语从句表示比较或方式时，从句中的谓语动词用虚拟语气。动词形式用动词的过去式(be→were)或had+过去分词。如：

The teacher treats the student as if he were her own child. 这位老师带这位学生就象她的亲生孩子一样。

He speaks as if he had been to the United States. 他说得好象他真的到过美国似的。

（2）在It is time (that) …; I'd rather (that)…句型中从句的谓语动词常用动词的过去式表示虚拟语气，意思是“该干某事了，时间已经有些晚了”“我宁愿/希望”。如：

It is time that we did something to stop pollution. 该我们做些什么制止污染的时候了。

It is time that Father picked up Lily from the kindergarten. 该父亲去幼儿园接莉莉的时候了。

I'd rather you told me the truth. 我真希望你告诉我真相。

I'd rather I didn't see you again. 我宁愿不再见着你。

5.虚拟语气在同位语从句中的用法

在名词advice, suggestion, order, proposal等后接的同位语从句中，谓语动词用虚拟语气，起形式为“(should)+动词原形”，说明“建议”，“劝告”，“命令”等的具体内容。如：

The order came that the work should be finished two days ahead of time. 提前两天完成工作的命令传来了。

Reluctantly she accepted their proposal that she should be operated on. 她勉强接受了他们要她去接受手术的建议。

难点释疑：

（一）主从句时间不一致情况下的虚拟语气（混合条件句）有时条件从句中的动作和结果与主句中的动作，发生的时间不一致，这时动作的形式应根据它所表示的时间加以调整。如：

If you had followed my advice, you would be able to finish the work now. 如果你当时听了我的话，现在就能完成这份工作了。（从句说明过去，主句说明现在。）

If I were you, I would have gone to her birthday party. 如果我是你，我就去参加她的生日晚会了。（从句说明现在，主句说明过去。）

If you hadn't lent me some money, I couldn't have bought the new house and most likely I would be still living in the dangerous house now. 假若你不借钱给我，我不可能买下这幢新房，很可能现在还住在危房里。（从句说明过去，主句说明过去和现在。）

（二）含蓄条件句非真实条件句中的条件从句有时不表出来，只暗含在上下文中，这种句子叫做含蓄条件句。含蓄条件句大体有三种情况；

1. 条件暗含在短语中。如：

(1)W hat would I have done without you? 如没有你，我会怎么办呢？（条件暗含在分词短语without you中）

(2) It would be easier to do it this way. 这样做会比较容易。（条件暗含在不定式短语to do it this way中）

(3) This same thing, happening in wartime, would lead to a disaster. 同样的事，如发生在战时，就会酿成大祸。（条件暗含在分词短语happening in wartime中）

(4) But for your help we couldn't have succeeded in the experiment. 如果没有你的帮助，我们的实验是不会成功。（暗含条件是but for your help）

(5) He must have the strength of a hippopotamus, or he never could have vanquished that great beast. 他一定是力大如河马，否则他绝不会击败那只庞大的野兽。（暗含条件是连词or）

(6) Alone, he would have been terrified. 如是单独一人，他是会感到害怕的。（暗含条件是alone）

（三）条件从句中省去if的情况在if引导的表示虚拟的条件状语从句中，常可以省略if，将had, were或should提至句首。

Had I seen the film, I would have discussed it with them last night. 假如我看了那部电影，昨晚我就可以和他们一起讨论了。

Were I a bird, I could fly freely. 假如我是一只小鸟，我就能自由翱翔。

Should it rain next week the farmers would have a good harvest. 要是下周能下雨的话，农民们就能有个好收成了。