高三英语语法复习虚拟语气一、条件结果关系的虚拟语气在含有条件的虚拟语气结构中，通常主句是结果，从句是条件。
按照现在、过去和将来三个不同的时间，分别有对应的动词形式。
If he were here, everything would be all right.If it weren’t for their support, we would be in a very difficult position.If I were you, I might tell him the truth.I would /could /might certainly go if I had time.How nice it would be if you could stay a little longer!If I had left a little earlier, I would have caught the train.She could have come if she hadn’t been so busy.If I had had the money last year, I would /might / could/ should have bought a house.If I were to ( should ) do it, I would do it in a different way.If there should be something wrong, they would let you know at once.We wouldn’t lose courage even if we should ( were to ) fail again.4. 错综时间条件句带条件从句的虚拟语气，主句和从句的时间可能不完全一致，这时主句和从句的谓语动词要根据各自所指的不同时间选用适当的虚拟语气形式。
这种句子被称为错综条件虚拟语气，或混合时间虚拟语气。
如：He would be dead now if the doctor had not operated on him right away.If I were you, I wouldn’t have missed the film last night.If you were in better health, we would have allowed you join them in the work.If we hadn’t been working hard in the past few years, things wouldn’t be going so smoothly.If my grandfather were alive, he would have been 100 next year.5. 含蓄条件句有时，虚拟条件不一定是由if引导的条件从句，而是其他形式，或者可能根据上下文省略了条件，或者隐含在文字中，这种条件虚拟语气，称为含蓄条件虚拟语气。
这时表示结果的句子要根据自身的时间来确定动词的形式。
If not for their help, the situation would never have been what it is today.（省略句）Born in better times, he would have achieved more in science.（过去分词表示条件）He would be stupid not to accept that suggestion.（不定式表示条件）This same thing, happening in wartime, would amount to disaster.（现在分词表示条件）Without power, there would be no modern industry.（介词短语表示条件）But for the storm, we should have arrived earlier.（介词短语表示条件）We would have done better under more favorable conditions.（more隐含条件）A less difficult problem would have been solved.（less隐含条件）That would have been considered a miracle in the past.（in the past如果在过去）I was ill that day. Otherwise I would have attended the lecture.（otherwise 如果不是这样）We would have given you more help, but he has been so busy.（事实反衬虚拟条件）Anyone else in my position would have done the same.（else隐含条件）A different word would have settled the quarrel.（different隐含条件）Another inch forward, and the snake would have struck.（如果再向前一点点）二、状语从句中的虚拟语气1. 让步条件状语从句中的虚拟语气：even if /even though引导让步条件，主句和从句都用虚拟语气，动词形式分别对应于带条件从句的主句和从句。
如：Even if my mother were here, I would /should say the same thing.Even though it had been a rainy day, I should have gone to see him.2. 方式状语从句中的虚拟语气：as if /as though引导方式状语从句，如果是非真实的情况，也使用虚拟语气。
He treats me as if I were a stranger. （从句动词与主句时间相同）He talked as if he were the witness himself.（从句动词与主句时间相同）They talked as if they had been friends for years.（从句时间先于主句）Why is she looking at me as though she had seen me before? （从句时间先于主句）三、虚拟语气在名词性从句中的应用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、或对于将来的主观愿望，从句通常省略连词that。
should可以省略。
如：I propose that we (should ) set a dead line for handing in the plans.He insisted that we take up the matter at the meeting.He ordered that the letter be mailed at once.The law r equires that everyone take a test for a driver’s license.I think it advisable that he have his car serviced.The United Nations urged that he withdraw his troops.I move / recommend that he go there.常用于主句的谓语动词有：ask, decide, demand, desire, insist, move, order, prefer, propose, request, require, suggest, urge, instruct, persuade, dictate, determined, beg, advise, resolve, intend, argue, maintain, deserve, promise, arrange，等。
以上动词改为被动语态之后，成为It is / was that…的复合句，原来的宾语从句变为主语从句，原有的谓语动词仍然为should +动词原形，should可以省略。
如：It is requested that Mary should give a performance at the party.It is desired that we get everything ready by tonight.It has been decided that the meeting be postponed till next Friday.以上动词如果有对应的形容词，做表语时，其主语从句也有同样的虚拟语气要求；以上动词对应名词的同位语从句，也有同样的虚拟语气要求。
3. It is + adj. that结构中，that为主语从句，从句中的动词用should + 动词原形，表示“应当”的意思，should可以省略。
这类形容词常见的有：compulsory, crucial, essential, obligatory, urgent, necessary,以及表示命令、建议、要求等意义的形容词。
It is important that unite with all that can be united in the work.It is necessary that he be sent there at once.4. It is + adj. that结构中，that为主语从句，从句中的动词用should + 动词原形，should表示惊讶、失望、欣慰、疑惑等语气，不可以省略。
It is a great pity that he should be so conceited.It’s strange that she should have failed to see her own shortcomings.It was extraordinary to me that you should have seen this.It is no wonder that he should be so angry.He just couldn’t believe that the new stadium should be so large.I am sorry that he should be in such poor health.We were surprised that he should be so stubborn.I am still not quite convinced that she should have done so much in such a short time.四、其它句型中的虚拟语气1. 在would rather, would sooner, had better, would as soon, just as soon 的句型中，接动词原形，指现在和将来时间，表示一种主观愿望和选择。