if用法详解(二)if 非真实条件句

一、概念

①虚拟语气

英语中的语气分为陈述语气、祈使语气、虚拟语气、疑问语气和感叹语气五类。

其中虚拟语气是说话者用来表示假设，或难以实现的情况，而非客观存在的事实，所陈述的是一个条件，不一定是事实，甚至完全与事实相反。

此外如需表达主观愿望或某种强烈的感情时，也可用虚拟语气。

②非真实条件句

非真实条件句同时也叫虚拟条件句,即虚拟语气在条件句中的应用，表示与现实情况相反或发生几率非常小的假设情况。

虚拟语气表示主观的假设、想象，用来谈论非真实的情况，即不可能发生的事或难以实现的情况，所陈述的是一个假设条件，而非事实。

虚拟语气也可以用来表示主观的愿望或强烈的情感等等。

I am rich, so I can buy a car.

【“我有钱”是事实 】

If I were rich, I could buy a car.

【"我有钱“是假设条件，事实是“我没钱”】

I wish I were rich.

【“我有钱”是愿望】

二、分类

1.时间型条件句

A.单一时间型

①与现在事实相反

句子结构为：

从句：If+主语+动词一般过去时(be多用were)

主句：主语+ should/would/might/could+do

If I had enough money, I would buy that new toy for you.

如果我有足够的钱，我就会给你买那个新玩具。

If there were no air or water，there would be no living things on the earth.

如果没有水和空气，地球上就不会有生物。

②与过去事实相反

句子结构为：

从句：If+主语+had done

主句：主语+should/would/might/could+have done

If I hadn’t been ill yesterday, I might have come to school.

昨天要是不生病，我是可能来上学的。

If I had made good preparations, I wouldn't have lost the job.

如果我做了充分的准备，就不会失去这份工作。

③与将来事实相反

句子结构为：

从句：①if+主语+were to do②if+主语+should+do

③if+主语+动词一般过去式(be动词用were)

主句：主语+should/would/might/could+do

If it should rain tomorrow, I would stay at home. 

如果明天下雨的话，我将待在家里。

If you succeeded, everything would be all right. 

如果你将来成功了，一切都会好的。

④当if引导的非真实条件句中含有were，had或should时，可省略if，并将were，had或should放在主语前面，形成倒装，详见下文4.省略倒装型条件句。

B.错综时间型

一般情况下，虚拟条件句中主从句的谓语动作时间是一致的，但如果不一致，则根据具体语境作相应的调整。

①从句动作与过去事实相反，主句动作与目前正发生的事实相反

If I had taken my raincoat with me this morning, I would not be wet now.

如果今天早上我把雨衣带在身上，现在就不会湿了。

If he had been working hard, he would be working in the office now.

要是他工作一直努力的话，他现在已进了办公室了。

②从句的动作与现在事实相反，主句的动作与过去事实相反。

If he knew her, he would have greeted her.

要是他认识她的话，他肯定会去问候她了。

If he were free today，we would have sent him to Beijing.

如果他今天有空的话，我们就已经派他去北京了。

注：条件从句用 if I were…时，既可指现在也可指过去。如：

If I were you, I would go.

假若我是你，我就去。

If I were not busy, I would have come.

若不忙，我早就来了。

也可用 if I had been you表示过去：

If I had been you，I’d have taken the job.

我要是你，我就接受那份工作了。

2. 无条件型条件句

(1)也称隐含式条件句或含蓄虚拟条件句，即没有直接给出假设情况的条件，而须通过上下文或其他方式来判断。如：

I would have come to see you, but I was too busy.

我本该来看你了，然而我太忙了。

But for his help, we would be working now.

=If it weren’t for his help, we would be working now.

要不是他的帮助，我们还会在工作呢。

Without your instruction, I would not have made such great progress.

要是没有你的指导，我不会取得如此大的进步。

(2)可以表示无“条件”的词或短语：

with/without, or, or else ,but, otherwise, even, but for, except for, only(that),  what if 等。

(3) 隐含类型

(a) 将条件隐含在某些连词中：

I didn’t know that he was a cheat, or else I wouldn’t have believed him.

=I wouldn’t have believed him, but I didn’t know that he was a cheat.

= If I had known he was a cheat, I wouldn’t have believed him.

我不知道他是个骗子，不然我也不会相信他了。

She wasn't feeling very well. Otherwise she wouldn't have left the meeting so early.

她不是很舒服。不然的话，她不会那么早离场。

(b)If it weren’t for/if it hadn’t been for若不是(有); 要不是有

If it weren’t for /Without water, no plant could grow.

要是没有水植物就无法生长。

If it hadn’t been for /But for the doctor, he would have died.

要不是医生救了他，他就会死了。

(c) 将条件隐含在介词(短语)中：

Without air, no one could live.

=If there were no air, no one could live.

没有空气，人就不能活。

But for his help,,we couldn’t have done it better.

要不是他的帮忙，我们本不能做得更好。

     (d)将条件隐含在分词短语中：

Born in better times, he would have been a scholar.

=If he had been born in better times, he would have been a scholar.

如果出生在好时代，他早就成为学者了。

Failing this time, what would you do？

=If you failed =this time, what would you do？

假若这次失败，那你怎么办？

       (e)将条件隐含在名词短语中：

A true friend would not have betrayed me.

=If he had been a true friend, he would not have betrayed me.

若是真正的朋友，就不会背弃我。

A few hours earlier, and you would have seen the famous writer.

=If you had come a few hours earlier, you would have seen the famous writer.

=Come a few hours earlier and you would have seen the famous writer.

要是早来几个小时，你就见到这位著名的作家了。

(f) 将条件隐含在定语从句中：

Anyone who had seen that painting might have taken it for a photo.

=If anyone had seen that painting，he might have taken it for a photo.

凡是看过那画的人，都可能把它看成是照片。

3.半分裂型条件句

有时虚拟条件句中,省略主句或从句来表示说话人的一种强烈感情。如：

He would have finished it.

他本该完成了。

If only I had got it.

要是我得到它了该多好啊。 

4.省略(倒装)型条件句

(1) 省略if

当虚拟语气在非真实条件句使用时，如果含有 should、had、were或其他助动词，则If可以省去，此时非真实条件句就要进行倒装，即把were，had，should提前放句首，以强调假设条件的虚拟性或突出说话人的主观愿望。

注：

① 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而置于句首。如：

Were I not Tom, I would refuse.

如果我不是汤姆，我会拒绝的。

Should it not rain tomorrow, I would go shopping.

明天不下雨，我就购物。

② 有时省略if后提前的had不是助动词：

Had I time(=If I had time…), I would come.

假若我有时间，我会来的。

③在虚拟条件从句中，动词“be”的过去时态一律用”were”

If it weren’t for water, no plant could grow.

=Were it not for water, no plant could grow.

要是没有水植物就无法生长。

(2) 省略”主语+be”

若主从句主语一致，且谓语部分包含有动词be，通常可将主语和动词be省略：

If (it had been)repaired earlier, the tractor would not have broken down.

要是早点儿修一下，拖拉机就不会抛锚了。

(3) 省略“it+be”：

If (it is) necessary, I would send more farm-hands to help you.

如果需要的话我会派更多的民工去帮你。

(4) 省略“there be”：

If (there were) any,fetch me some drink.

要是有喝的，给我拿点来。