和could的区别用法_虚拟语气用法总结
老师叮咛：李辉老师说，语法填空这种题型，考点极其固定，因为百年以来英语语法都没发生过巨大的变化。高考语法考点本来就有限，能用填空这种形式来考的语法考点就更有限了。只要掌握知识点，考试必须妥妥的！下面的虚拟语气“很重要”！经过了全网首席高考英语名师李辉老师团队高度认真的整理校对，无错，可信！可供全国各省高中生打印、学习、背诵！
一、语气概述
时态语态一样，语气也是谓语动词的一种形式，它表明说话者的目的和意图。英语中有三种语气：陈述语气，祈使语气和虚拟语气。（有的语法书说语气有四种，即还包括疑问语气）。
eg:
①He doesn’t see very well in his right eye. 他右眼视力不太好。（陈述语气）
②Have they ever been to Australia ? 他们去过澳大利亚没有？（疑问语气）
③Please read through the instruction in advance. 请先通读说明书。（祈使语气）
二、虚拟语气概述
在英语中，由于说话人的意图不同，动词需用不同的形式，称为语气。虚拟语气是指说话人表示一种假设的情况，一种愿望，怀疑，推测，请求等，即认为动词所表示的动作或状态并非事实。虚拟语气可用于状语从句，名词性从句，定语从句及其他结构中。
三、虚拟语气的定义
如果一件事不是真实的，而是虚拟的，就在这个动词身上加一个did。
四、非真实条件句中的虚拟语气
以下为If在非真实条件句中虚拟语气的形式和用法：
假设类型If从句主句与现在事实相反did(be用were)should / would /could / might+do与过去事实相反had doneshould / would /could / might+have done与将来事实相反1)did2)were to do3)should doshould / would /could / might+doeg:
①If I were you ,I would reconsider their advice.
如果我是你的话，我会重新考虑他们的意见。（与现在事实相反）
②You would not have caught a cold if you had put on more clothes.
如果你多穿了些衣服，你就不会得感冒了。（与过去事实相反）
③If I were to / should do it ,I would do it in different way.
如果我做这件事，我将用不同的方法做。（与将来事实相反）
注意：在非正式文体中，如果If 条件句中有助动词were / should / had可将其提于主语之前（位于句首），再把If省掉，即形成部分倒装。
当主从句所表示的时间不一致时，主从句按各自的时间采用相应的谓语形式。
常见的有：
①If I were you ... = Were I you ... 如果我是你/我要是你......
②If it were not for ... = Were it not for ... 如果要不是......
③If it had not been for ...=Had it not been for ... 如果当时要不是......
（③主句用：should / could / would / might + have done的形式，ps.在此结构中，had为助动词。若为谓语动词，则不能省略、倒装。）
B.错综时间条件句
主句和从句不是一个时间平台，需要分别在三个时间平台里“选形式”。
从过完用had done，主过将用would do
从用should / were to，主过将完用would have done
eg:
①If the weather had been more favorable ,the crops would be growing still better.
如果天气更好的话，庄稼就会长得跟好些。（从句指过去，主句指现在）
②If I were you ,I would have taken his advice.
我要是你，我就采取了他的建议。（从句指现在，主句指过去）
C.含蓄虚拟条件句（if省略句）
有时假设的情况不以条件句的形式表现出了，而是通过一个介词短语或分词或其他方式表现出来。当虚拟条件句的谓语动词含有were / should / had 时，if可以省略，这时条件从句要用倒装语序，即把were, should, had等词置于句首，这种多用于书面语。
(1)省略if
Step1:去掉if。
Step2:助系情提到主语之前。
•Were I you, I would go.
•Had I known about the party, I would have come.
•Should I go abroad, I would buy you a gift.
注意：在虚拟主句中，主语只有是第一人称时，才能用should。
(2)根本没有if
有些句子里，没有if，但是有but for（若不是）/ without / under / otherwise / but / or / but that（若不是）等，此时可把它们看做虚拟条件句，然后根据时间平台，选择主句的动词形式。
• Without your help, I wouldn’t have passed the exam.
= If you didn’t help me, I wouldn’t have passed the exam.
=But for your help, I would not have passed this exam.
• I don’t have your telephone number, otherwise / or I would have called you back.
= If I had your number, I would have called you back.
• What would you do with a million dollars?
=What would you do if you had a million dollars?
D.wish,as if / though和if only用法
(1)wish用法如下：
1.表示与现在相反的愿望: 主语 + wish (that)...did (were)...
eg: I wish I were a bird.
2.表示与过去相反的愿望: 主语 + wish (that)...had done...
eg: I wish I had seen the film.
（注意：如果wish在表达对过去情况的虚拟而不是未实现的愿望时，有
时也可用: 主语+wish(that)...would / could have done）
3. 表示与将来相反的愿望: 主语 + wish (that)... could / would / might do
eg: I wish you would do that again.
(2)由as if/though引导的表语从句
(3)If only...引导的条件句
（常用感叹的形式）表示强烈的不满，遗憾或愿望，主句常省略，意为：“要是/如果......该多好啊/就好了！”。（注意：“only if ...”意为：“只要......”，位于句首时采用部分倒装。）
结构简图：
表虚拟的时间if only 从句谓语形式现在did（be动词用were）过去had+done将来would / could / might+doeg:
①If only I could see him once more ! 我要是再见到他就好了！
②If only we had telephoned him in advance ! 要是事先给他打个电话就好了！
E. Suppose / Supposing / providing / provided (that)... / what if...等某些特殊的连词后引导的条件句中（有时无主句），表示与现在或将来事实相反用did；表示与过去相反用had done。
eg:
①Suppose / Supposing (that) we told her the truth.
假定我们把事情的真相告诉她。
②What if you came tomorrow instead of today.
如果我是你明天来而不是今天来呢？
F.would rather后的宾语从句：表示愿望或尚未发生的动作。
had / would sooner / rather + that...从句中意为“宁愿”，用did（be动词用were）表示对现在或将来的虚拟；用had done表示对过去的虚拟。
eg:
①She will get home at dinner time, but I would rather she got home a little earlier.
②He got drunk last night. I’d rather he hadn’t drunk so much.
五、名词性从句中的虚拟语气（should类虚拟语气）
即主句含有：建议、命令、请求、要求、愿望、主张等意思时，后面的从句用(should)+V原 / should have done的形式。但注意，若从句中含有“竟然，惊讶，诧异”之意时，“should”则不可以省。
（常见简记：一坚持，二命令，三建议，四要求）其他同下述用法：urge / propose
eg:
①The teacher suggested that we (should) make good use of every minute.
②He ordered that all the book (should) be sent at once.
③She insisted that she (should) go to the south for her holiday.
注意：
六、副词性从句中的虚拟语气
A.as if / though用法
虽同wish ，但也有一些区别，如下：
as if / though 从句时态不受主句限制 。
①在谈论现在情形时用一般过去时。
②在谈论过去情形时用：
Ⅰ.一般过去时：表示过去当时存在的某种状态，但若状态动词后带有持续的时间状语，则要用过去完成时。
eg:
①They talked as if they had been friends for years.
他们谈起话来，好像是多年的朋友。
②He looked at me as if I were mad.
他看着我，好像我疯了似的。
Ⅱ.过去完成时： 表过去的动作先于主句而发生，即使主句是现在时，as if 从句中的谓语动词也要用 had done。
eg: It seems as if it had gone bad.
它闻起来好像坏了。
③在谈论将来情形时用： would (could/might)+do
http://B.in case / lest / for fear that 表“以防，以免”等引导的目的状语中的虚拟语气，其后的形为：(should)+
V原 （但注意in case 句中的should通常不省）。若不用虚拟也可用陈述，即用： 一般现在时或过去时。
C.even if / though “即使/纵然/虽然”
七、形容词性从句中的虚拟
八、虚拟语气固定句型
1. Would you mind+主语+谓语虚拟？ 您是否介意…?
2. would rather (that)主语+谓语虚拟 宁愿…
3. It is high time that sb. did / (should) do sth. 到某人做某事的时间
4. It is necessary / important / essential / strange / natural /advisable / surprising that sb. (should) do sth.
5. It is a pity / duty / shame / regret that sb. (should) do sth.
6 But for / Without + sth. +主语+谓语虚拟 要不是…
7. If only+主语+谓语虚拟 要是…就好了！
8.主句+ as if / as though +主语+谓语虚拟 就好像…
九、情态动词+have done
could / might have done 本来能做却没做
should / ought to have done 本该做而实际上没做（抱怨和责备）
should not / ought not to have done 本不该做而做了
needn’t have done 本不必做而做了
十、虚拟语气的其他用法
(1)表示过去本打算做而实际上没有做。
句型： had done (be / intend / think / mean / plan / hope etc) to do
= V-ed + to have done ,would love / like to have done
(2)had hoped 表过去未实现的愿望，译为“要想，希望…”，从句谓语常用“would +V原”。
eg: He had hoped that the family would come before his granny came. ———2013年湖北高考
(3)may(might) as well + V原 ，译为“不妨，倒不如”，表示劝说、建议、劝告。
若其后带有某种消极情绪时，常用：might.
(4) 表示祝愿、命令的简单句中。常用“may +主语+动词原形”。
eg:
①Long may you live.
②May you have a good journey!
(5)表示对过去事情的懊悔时，谓语用“should + have + 过去分词”。
eg: You should have returned the money to Mary.
十一、虚拟语气解题常用技巧
1. 找固定句型。
2. 主过将从过；主过将完从过完。
十二、虚拟用法形式总结
含三种：
①所有含if的从句（除what if…外）。
②wish从句。
含两种：
①某些特殊连词后的条件句。
②what if…从句。
③would rather从句。
④定从中的虚拟。
含一种：
①含蓄虚拟语气（情+have done / do）。
②名词性从句（除wish外）与表“以防”意义的条件句中的虚拟一样(should+V原)。