虚拟语气

具体查阅张道真语法指南。

5、倒装: 当从句的谓语动词含有were，should，had时，if可以省略，这时从句要用倒装语序，即把were，should，had等词置于句首，这种多用于书面语。eg¹：
Were I Tom, I would refuse. = If I were Tom, I would refuse.
如果我是汤姆，我会拒绝。
Should it be necessary, I would go.
假若有必要，我会去的。
Had it not been for the bad weather we would have arrived on time.
若不是天气坏，我们就准时到达了。
Should he agree to go there, we would send him there.
要是他答应去的话，我们就派他去了。
Were she here, she would agree with us.
如果她在这儿的话，她会同意我们的。
Had he learnt about computers, we would have hired him to work here.
如果他懂一些电脑知识的话，我们已经聘用他来这里工作了。
【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。
② 有时省略if后提前的had不是助动词：
Had I time, I would come. 假若我有时间，我会来的。(=If I had time…)

Footnotes

1. abbreviation for exempli gratia: a Latin phrase that means “for example”. It can be pronounced as “e.g.” or “for example”.例如（exempli gratia的缩写，可以读作 e.g.，也可读作 for example） You should eat more food that contains a lot of fibre, e.g. fruit, vegetables, and bread. 你应当多吃些富含纤维的食物，例如水果、蔬菜和面包。 ↩