虚拟语气的语法结构是什么

虚拟语气分为条件虚拟和愿望虚拟两大类，简单介绍如下——

一、条件虚拟

1、由连词引导的条件从句，常用的有：
* if/unless 如果/若非
* 3. even if / even though 即便
* in case：万一，如：
--You should bring an umbrella with you, in case it were raining; of cause there’s no rain today

2、省略 if 后的倒装虚拟，如：
* Were I you, What should I do?
* Had he been here five minutes earlier, he would have caught the train.

3、相关动词分词或短语充当连词
* 过去分词： provided，如：
--*We would pay the bonus provided the job had been completed on time yesterday. 如果工作在昨天按时完成的话我们会发放奖金的。
* 动词原形：suppose (that)，如：
--Suppose (that) I were you. 要是我是你多好）。
* 现在分词：supposing，如：
--Supposing it were not Saturday tomorrow. 假如明天不是星期六（就好了）

4、介词 without 短语表示的条件，如：
--Without electronic computers, much of today's advanced technology would not have been achieved. 要是没有电脑的话，就不会取得当前这么多的先进技术

5、but tha t除非,若不是，如：
--They would have got in touch with us two days earlier but that there had been something wrong with the line. 若不是线路有问题的话，他们两天前就与我们取得联系了。

二、愿望虚拟

1、名词从句

1）提出建议、发出命令、提出请求、表示见解愿望，下面以suggest及其派生词为例：
宾语从句：I suggested that he (should常常省略) leave immediately.
表语从句：My suggestion is that he leave immediately.
主语从句：That he (should) leave immediately is my suggestion
同位语从句：My suggestion, that he leave immediately, has not been adopted.

2）用在it is … that 句式表示上述意思，如：
--It is important that he that he (should常常省略) leave immediately.

2、几种特殊的虚拟句式
* wish 从句，如：
-- I wish he knew what is happening there in his room. 要是他知道自己的屋子里正发生着什么就好了。（对此时此刻的虚拟）
--He wished he hadn't done it. 他想要是他没这样做该多好。（对过去的虚拟）
* would rather 从句
--I would rather you (should) come tomorrow.（对将来的虚拟）我宁可你明天过来（暗含你却来不了。）
* it is time 从句
--It is high time you had got up to have your meal. 你早就该起床吃饭了。（但是到现在你还没起来）
* had better 从句
--His mother had better he would have come the next day. 他母亲宁愿他第二天过来。

三、套式虚拟句

在表达某些信条的陈述或信仰的自白的时候，常用套式虚拟句。在这种虚拟句中，谓语动词不受人称和时态的约束，只以动词原形出现在句子中。以下是常见的套语：

1. 表示祝福
* God belss you 上帝保佑
* God bless my life / my soul! 我的天啊! 好家伙!
* God speed you! 祝你一路平安!
* Long live liberty! 自由万岁
2. 表示诅咒
* God damn you! 天杀的! 该死的!
* God forbid! / Heaven forfend!苍天不容! 但愿不会如此!
3. 表示发誓
* Far be it from me to … 我决不会…
* Suffice it to say that … 只要说…就够了。
* Come what may / will … 不管发生什么事情
4. 表示愿望
* God grant ...! 但愿...!
* So be it then. 那样也好
* Be that as it may … 尽管这样
5. 表示感叹
God help him! 唉, 真可怜!
Heaven help us! 苍天保佑！

关于虚拟语气的时态问题

一、条件虚拟句或特殊句式的虚拟
1、对现在的虚拟
* 主句 —— would/should/could/ought to + 动词原形
* 从句 —— 动词过去形式（动词 be 一律用 were）
2、对过去的虚拟：
* 主句 —— would/should/could/ought to + have done
* 从句 —— 过去完成式 had done
3、对将来虚拟，分三种情况：
1）实现的可能性不大 ——（should可省略，但是要注意只能用should 而不可以用其他情态动词）do；
2）实现的可能性很小 —— 过去时（did/were）
3）根本不可能实现 —— were to do

二、名词从句中的虚拟一律用“should + 原形”或者省略 should 直接用动词原形