一、非真实条件句

1.非真实假设

1. 与现在事实相反

   一般过去时+would do

   If I had time, I would go to the movies with you.

2. 与过去事实相反

   had done+would have done

   If we hadn't made adequate preparations, the conference, wouldn't have been
   so successful.

3. 与将来时间相反

   should/were to+would do

   should：有可能发生，但主观不希望发生。

   were to：不大可能发生。

   If it were to rain tomorrow, the game would be put off.

4. 引导非真实条件从句的连词if在正式文件中有时可以省去, were, had,
   should等非行为动词这时应提到从句句首。

   If I were you, I wouldn't feel sorry.
   Were I you, I wouldn't feel sorry.

2.as if/as though

as if/as though 就好像···

引导让步状语中的虚拟语气。

在as if (though) 引导的状语从句中, 谓语动词有时用虚拟式。

陈述句：

He speak English as if/as though he is from the USA.

虚拟语气：

He speak English as if/as though he were from the USA.

例句：

She looks as if she knew all about it.
They talked as though they had got acquainted with each other for years.

3.混合条件句

主从句时间不一致情况下的虚拟语气叫做时间错综复杂的状语从句，也叫混合条件句，这时动作的形式应该根据它所表示的时间加以调整，即各论各的。

4.含蓄条件句

非真实条件句的条件有时不表示出来，暗含在上下文中。

What would i have done without you?

二、名词性从句中的虚拟语气

1.主观倾向性动词

主观倾向性引导的宾语从句要用虚拟语气以（should）+do的形式出现

1. I suggest that we (should) go camping tomorrow.

2. He insisted that our laboratory reports (should) be handed in the day afterthe experiment was done.
   他坚持要求我们在做完实验后第二天将实验报告交上来。

3. He asked that they (should) be allowed to use a dictionary.他要求准许他们用词典。

4. The director required that we should work all night主任要求我们通宵工作。

5. The mayor ordered that free food be distributed.市长命令发放免费食品。

6. The boss demanded that Mary (should) finish it within a week.老板要求玛丽在一周内完成它。

7. I propose we should have another meeting. 我提议我们再开一次会议。

8. I command that he go at once.我命令他立即就去

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注意,以上句中insist意为“坚持要求”，suggest意为“建议”。如insist作“坚持认为”或suggest作“暗示”,
则不需用虚拟式。
He insisted that he was right.
他坚持认为他是对的。

2.wish

虚拟式可用于wish后的宾语从句中, 表示与事实相反的愿望。

主从：

1. wish+that···
2. how i wish···

从句：

I wish I had been to the concert last night.
I wish he would forgive me.

3.It is + 主观倾向性动词+that···

It is requested that all the students wear school uniforms at school.

4.主观倾向性动词的名词形式

主观倾向性动词的名词形式后面的表语从句或同位语从句也应用`should+do

My suggestion is that you go home first before coming here.

My suggestion is that we finish the task immediately.

三、虚拟式也可用于其他情况

1.would (had) rather

在I would (had) rather后的句子中, 动词也要求用虚拟式, 表示某人的愿望。

I'd rather you left tommorrow instead of today.
I'd rather he hadn't done anything like that.

2.It's (high, about) time that…

It's (high, about) time that…的句型要求用虚拟式,
表示应该做还没做的事。((时节)正盛的;(时机)成熟的)

It's high time that he stopped smoking.
It is high time you made up your mind.你该拿主意了。
It's about time that we took our leave.

3.but for/without/oterwise/supposing

有些句子从表层结构上看无if引导的非真实条件句,但从深层意思上看是存在的。这种情况下主句动词仍需用虚拟式。

这类句子中常出现without(如果没有), but for(要不是),otherwise(否则), but that(若不,后接一从句)等词或词组。

But for your help, they couldn't have succeeded.
要不是你的帮助, 他们就不会取得成功。
She wasn't felling well. Otherwise she wouldn't have left the meeting so early.
她感不舒服。不然她不会那么早就离开会场的。

4.if only

if only 引导的句子用虚拟语气

If only I knew his name now!

5.it's necessary that...

在it's necessary (important, natural, essential, proposed, required,suggested, impossible, strange)that…引导的真正的主语从句中动词应用虚拟式,表示必要、应该、建议、要求、惊讶、不相信等意。

It's necessary that we (should) set out at once.
It's proposed that a committee (should) be set up to look into the matter.
It's only natural that you should be nervous. 你感到紧张是很自然的。
The dentist suggested that she (should) come another day.
It is highly important that we (should) combine revolutionary sweep with
practicalness. "对我们来说,把革命气概和实际精神结合起来是很重要的。"
It is impossible that he should have missed the train. 他不可能误车。
It's strange that he should have failed in the exam.