第一章、虚拟语气在非真实条件句中的用法1. 非真实条件句中谓语动词的形式 条件从句结果从句与现在事实相反If I (we,you,he,they)+ 动词过去式(be的过去式用were)I(we) should.You would. He would .They would+动词原形与过去事实相反If I (we,you,he,they)+had+过去分词I(we) should.You would.He would .They would +have+动词原形与将来事实可能相反If I (we,you,he,they)+ 动词过去式(be的过去式用were)/were to/shouldI(we) should.You would. He would .They would +动词原形 但要注意：美国英语的结果主句，不管什么人称，皆常用would1在请求时,没区别如 Could you go with me? =Would you go with me?2在表示习性时，不用could ，用 wouldIpushed the door, but it wouldn't open. 我用力推门却推不开．3could用在wish的句型中： I wish I could go to the Moon.4 would ,could 都可以用在带if条件句的虚拟语气主句中，意思大致不变． If I had a lot of money, I would/could buy a set of house in Beijing.5 表示推测时，不用would She could have gone to the cinema .(她可能看电影去了）2. 与现在事实相反的非真实条件句虚拟语气用在与现在事实相反条件句中时，条件从句的谓语用动词的过去式 （be的过去式用were），结果主句的谓语用should(第一人称)或would(第二、三人称)＋动词原形。
如：I am sorry I am very busy now. If I had time, I would certainly come to see you. 很抱歉，我很忙如果有时间，我一定去看你了If it weren’t for their support, we would be in a difficult situation. 要不是有他们的支持，我们的处境会很困难if places were alike, there would be little need for geographers. 如果各个地方都一样，就不需要地理学家了If I were you, I would apply for the job. 如果我是你，我会申请那份工作的What would you do if you knew who broke the glass. 要是你知道谁打破了玻璃，你会怎么办？Even if I had the money, I wouldn’t buy it.即使我有钱也不会买它3. 与过去事实相反的非真实条件句虚拟语气用在与过去事实相反的条件句中时，条件从句的谓语用had＋ 过去分词，结果主句的谓语用should(第一人称) 或would（第二、三人称） ＋ have＋ 过去分词。
如：If I had taken your advice, I wouldn’t have made such a mistake.如果当时听了你的话，我就不会犯这样的错误了If it had not been for your help, I wouldn’t have finished the work so easily. 要不是你的帮助，我的工作不会这么容易完成If we had known the basic principles, we should have controlled the process even better.如果我们知道这些基本原理，我们早就能更好地控制这个工序了If facts had been collected one week earlier, we should have had more time to study them.假使早一个星期收集事实，我们就有更多的时间研究它们了The conference wouldn’t have been so successful if we hadn’t made adequate preparation.如果我们不做充分的准备，会议是不会开得这么成功的。
4. 与将来事实相反的非真实条件句（1）虚拟语气用在与将来事实相反的条件句中时，条件从句的谓语用动词的过去式（be的过去式用were），were to或should，结果主句用should(第一人称)或 would（第二、三人称）＋ 动词原形如：If it rained( were to rain/ should rain) tomorrow, I should stay at home. 如果明天下雨，我会呆在家里If the teacher knew it, he would be angry.万一老师知道了这事，他会生气的I wouldn’t lose courage even if I should fail again. 即使再次失败我也不会气馁If I made a mistake, I should try to remedy it. 假如我犯了错误，我就会设法补救If something should go wrong, the control rods would drop.万一发生什么事故，控制杆就会下落2) 在与将来事实相反的条件句中，其条件从句的谓语也可用were to ＋ 动词原形。
这种虚拟式比较正式，多用于书面语中，其假想性很强，实现性很小如：If I were to do it, I would do it another way.要是我来做这件事，我会用另一种方法If he were to come tomorrow, I would speak to him about it.假如明天他来，我会跟他谈这个问题5. 情态助动词用于虚拟语气有不少情态助动词也可用于虚拟语气如：May you live a long and happy life.愿你长寿幸福may只用于表示愿望）If there were no friction, an automobile could not move.没有摩擦力，汽车就不能开动But for your help, we couldn’t have succeeded.要不是你的帮助，我们是不会成功的If computers had not been invited, many problems on space flight could not have been solved.如果没有发明计算机的话，宇宙飞行的许多问题就不可能解决。
6. were， had， should等置于主语之前在书面语中，条件从句可以不用连词if，而将谓语中的过去式were，had或 should 等移至主语之前如：Were you in my position, what would you do?假如你处在我的位置，你会怎么做？Were he to leave today, he would get there by Friday.如果他今天动身，星期五前会赶到那儿Had some work been done, energy would have been applied.如果做了一定量的功，就一定消耗了能量Had they time, they would come to see you.如果他们有时间，他们就会来看你Should it rained tomorrow, the meeting would be postponed. 万一明天下雨，会议就会延期Should he come, he would be able to examine the trial run of the machine. 如果他来，他就能检验这台机器的试车情况了。
7. 条件从句与结果主句所表示的时间不一致(1) 当条件从句与结果主句所表示的时间不一致（如一个是过去发生的，一个是现在发生的）时，虚拟语气的形式应作相应的调整如：If you were in better health, we would have asked you to come. 如果你身体好一些，我们早就请你来了If we had consulted him on the question yesterday, we should know what to do now.假如昨天我们向他请教了这个问题，现在就知道该怎么办了You would be much better now if you had taken my advice. 假如你接受了我的意见，你现在就会好得多2) 如果条件从句用if I were．．．，结果主句则可用任何时间的虚拟形式如：If I were not busy, I would have come.假如我不忙，我就会去的were表过去）8. 虚拟语气在含蓄条件句中的用法(1) 条件暗含在短语中如：We didn’t know his telephone number; otherwise we would have telephoned him. 我们不知道他的号码，否则我们就会给他打。
暗含条件是otherwise）Without your help, we wouldn’t have achieved so much. 没有你的帮助，我们不可能取得这么大的成绩暗含条件是介词短语without your help）But for your help, I would not have succeeded in the experiment. 如果没有你的帮助，我的实验就不会成功暗含条件是but for your help）It would cause great trouble not to lubricate the bearing immediately. 不立即润滑轴承就会引起很大的故障暗含条件是not to lubricate the bearing immediately）Alone, she would have been terrified.(2) 条件暗含在上下文中如：I would not have done it that way.我是不会那么做的可能暗含if I were you）I was busy that day. Otherwise I would have come to help you.我那天很忙。
否则我会来帮你的可能暗含if I hadn’t been so busy.）You might come to join us in the discussion.你可以参加我们的讨论可能暗含if you wanted to）I would have bought the D。