Grammar in use-虚拟语气

语气是表示说话者对动词所表示的动作或状态的态度的一种动词形式。英语中有三种语气：直陈语气、祈使语气和虚拟语气。虚拟语气是表示说话人一种主观愿望、假想或建议。

一、真实条件和非真实条件

英语中的条件句分为真实条件和非真实条件。真实条件表示现实情况中可能实现的情况，而非真实条件表示与现实情况相反的假想情况。

（真实条件）如果工作条件不太差，我会接受这项工作。

If the working conditions are not too bad, I will accept the job.

（非真实条件）如果工作条件不太差，我就接受这项工作了。

If the working conditions were not too bad, I would accept the job.

（事实是The working conditions are too bad, so I won't accept the job.）

（真实条件）他说他如果失败，他还会再试一次。

He said if he failed, he would have another try.

（非真实条件）如果他失败的话，他会再试一次的。

If he had failed, he would have had another try.

（事实是He didn't fail and he didn't have another try.）

二、非真实条件句

1.与现在事实相反

If从句：动词过去时（be动词用were，但在口语中，在单数第一、三人称后也有用was。）

主句：would/should/could/might + 原形动词

如果房间大一点的话，我们就在那儿举行聚会了。

If the room were larger, we would hold the party there.

假如我身边有钱，我就借点给你。

If I had money on me, I would lend you some.

2.与过去事实相反

If从句：had + 过去分词

主句：would/should/could/might have + 过去分词

如果那个地方不远的话，我们就步行去那儿了。

If the place had not been far away, we would have walked there.

如果你仔细一点，这个错误是可以避免的。

If you had been more careful, the mistake might have been avoided.

3.与将来事实相反

If从句：should/were to/was to + 原形动词

主句：would/should/could/might + 原形动词

如果明天天气好，我们就继续收割庄稼。

If it should be fine tomorrow, we would go on with our harvest.

如果我们有足够的时间，我们可以讨论那个问题。

If we were to have enough time, we could discuss the matter.

有时if从句和主句所表示的假想情况时间不一致，如从句表示与现在事实相反，而主句表示与过去事实相反，那么句子两部分的动词形式也可以作相应的调整。

如果你身体好，我当时就让你接受那项工作了。

If you were in good health, I would have let you take that job then.

如果他早点出发，他现在已经到家了。

If he had set our earlier, he would be home now.

三、含蓄条件句

有时非真实条件句中并不出现if从句，假想的条件隐含在情景中或者其他语法手段表示，这种情况称为含蓄条件。含蓄条件一般可以用如下的语法手段表示：

任何人处于我的地位不会对这个想法产生兴趣。（非谓语形式）

Anyone being in my place wouldn't be interested in the idea.

聪明一点的人不会干那种事。（形容词比较级形式）

A cleverer man wouldn't have done that kind of thing.

我们在3天里完成了本来应该花6天完成的工作。（定语从句）

We finished the job which would have taken six days to finish in three days.

要不是机组人员，飞机就坠毁了。（介词词组= If it had not been for the crew, ...）

But for the crew, the plane would have crashed.

他不可能写信给我，否则我现在就收到他的信了。（上下文情景）

He can't have written to me. Otherwise I would have got his letter by now.

四、非真实条件句的倒装形式

非真实条件句if从句中若含有助动词should, had或者were，那么可以与主语倒装，但动词过去式不可以与主语倒装。

如果他在这里，他就会来帮助我们。

Were he here ( = If he were here ), he would come to help us.

Attention: 倒装结构中不能用was。

如果他吃过午饭，他不会吃那么多小甜饼。

Had he had lunch ( = If he had had lunch ), he would not have eaten so many cookies.

万一明天下雪，我们就推迟旅行。

Should it snow tomorrow ( = If it should snow tomorrow ), we would put off our trip.

某些动词后接宾语从句中的虚拟语气

Suggest, insist, demand等动词

Suggest, insist, demand, propose, require, ask, advise, order, request等动词后面的宾语从句中谓语动词须用虚拟语气，即（should）+ 原形动词。

将军命令他的部队开往前线。

The general ordered that his troops (should) move on to the front.

他们要求参观者在车间不吸烟。

They require that visitors (should) not smoke in the workshop.

虚拟语气同样适用于上述宾语从句转换生成的主语从句、表语从句和同位语从句。

有人建议每个人在聚会上作5分钟的发言。