b.若条件从句为否定句，否定词not应 置于主语之后，而不能与were，should， had等缩略成weren’t，shouldn’t， hadn’t置于句首。
1). If I had seen him then, I would have been very happy.
= Had I seen him then, I would have been very happy.
虚拟语气
虚拟语气的概念
虚拟语气：虚拟语气表示说话人的愿望、假
设或建议，而不表示客观存在的事实(不是事实 或不大可能发生的事情)。 虚拟语气通过谓语动词的特殊形式来表示。
高考中虚拟语气的常考形式：
1. if 引导的虚拟条件句 2. 名词性从句 3. 固定句式 4. 情态动词表示虚拟 5. 可用可不用虚拟语气的情况
三个建议，四个要求。 suggest
2. It is（necessary，strange…）+that… 1.过去式
1. wish/as if
2.过去完成
3.could、would、might +v
2. Would rather/ if only
1.过去式 2.过去完成
类似if型 3. It is (high) time that…
主语+would (
should / might / could )＋动词原 形
If+主语+had +动词的过 主语 + would (
去分词
should / might /
即：If+过去完成时态 could )＋have
done
1、If+主语+动词过去式 2、If+主语+were to+ 动词 原形
If I get up early, I will catch the train.
If I had got up earlier , I could have caught the train.
a. if真实条件句 表示条件是真的或 有可能实现的, 采用陈述语气。
b. if虚拟条件句表示对事实的相反的 假设，或是虚拟的或几乎无法实现的 , 采用虚拟语气。
与过去事实相反
If the foreigner had learnt how to swim, he would not have been trapped on the island for four years.
2.虚拟条件句中的倒装
a.在虚拟条件句中，如果条件句中有 were, had（助动词）或should时，可 使用倒装结构， were, had,或should 可 提前，if省略。
3、If+主语+should +动词原 形
主语+would (
should / might / could )＋动词原 形
If 型
。。。 。。。 。。。
混杂条件句(各自为准) Were, had ,should提前，省略if
Subjective mood
1. 一个坚持，两个命令， insist
Should +v型
2). If I should have time, I would go with you. = Should I have time, I would go with you. 3). If I were not so busy, I would go with you. = Were I not so busy, I would go with you.
与现在事实相反
If I were the schoolmaster , I would let the students get up a little later.
schoolmaster
if虚拟条件句 if虚拟条件句
主句
与将来 事实相 反的假 设
1、did 2、were to+ 动原 3、should +动原
would ( should / might / could )＋动原
与 将 来 事 实 相 反
If I met Obama some day, I would shake hands with him.
If I were to meet Obama some day, … If I should meet Obama some day, …
if虚拟条件句 if虚拟条件句
与过去 事实相 反的假 设
had +done
主句
would ( should / might / could ) ＋have done
与过去事实相反
If the boy had driven more carefully, he would not have caused the car accident.
Should（不省） +v/ 过去式
4. But for/otherwise/ without/in that case
1.Would,could,should,might+v
2.would,could,should,might
+have done
Period Four Grammar：Subjunctive (1)
1. if 引导的虚拟条件句
①与现在事实相反 ②与将来事实可能相反 ③与过去事实相反
if虚拟条件句 if虚拟条件句
主句
Hale Waihona Puke 与现在 事实相did
反设的假（be动词用were)
would( should
/ might / could )＋动原
与现在事实相反
If I had a great deal of money now, I would buy a big house for my parents.
虚拟语气(1) 动词的语气表示说话人的态度和看法，可分 为陈述语气、祈使语气和虚拟语气。陈述语气 用来陈述讲话人认为是事实的事情，有肯定、 否定、疑问和感叹等形式。祈使语气用来说明 说话人的请求、命令等。虚拟语气表示说话人 的愿望、假设或建议，而不表示客观存在的事 实。虚拟语气通过谓语动词的特殊形式来表 示。
语气
英语的动词一般可带有三种不同的语气： 陈述语气，祈使语气和虚拟语气。不同 的语气用动词的不同形式（有的还借助 句法形式）来表示。
与现在 事实相 反的假 设
与过去 事实相 反的假 设
与将来 事实相 反的假 设
if虚拟条件句
主句
If+主语+ 动词的过去式 （be动词一般用were)
即：If+一般过去时态 （be动词一般用were)