虚拟语气
1. if 引导的虚拟语气
if 表示如果：主句将来时，从句用一般现在时。
例1：如果明天下雨，我就呆在家里。
If it rains tomorrow, I will stay at home.
例2：如果我是个女的，就会…….
要点：不能实现，与事实相反，用虚拟语气
例如:
1、如果你早到一会，你就会赶上那辆公交车了。（与过去事实相反）
If you had got there earlier, you would have caught the bus.
2、如果没有空气的话，人就会死。（与现在事实相反）
If there were no air, people would die.
3、如果我有翅膀，我就飞过海洋去看你。
If I had wings, I would fly over sea to see you.
4、明天要是周日的话，我们就不参加考试了。（与将来事实相反）
If it were Sunday tomorrow，we wouldn’t have an examination.
相关练习：
1、如果我是你的话，我就会帮他。
If I were you, I would help him.
2、如果昨天你能来参加我的生日宴的话，你就能见到姚明了。
If you had come to my birthday party yesterday, you would have seen Yao Ming. 注意：错综虚拟语气：
例如：
如果你昨天听了我的建议的话（从句是与过去相反），你现在就知道该怎么做了（主句是与现在相反）。
If you had followed my advice yesterday, you would know how to do it now.
2. 倒装形式
if引导的虚拟语气中，如果出现了助动词had或者是were的时候，可以省略if,将had \were 提到主语前面。
Were I you (=if I were you), I would get up early in the morning.
Had you arrived at the station ten minutes earlier yesterday (=If you had arrived…),