If he hadn’t been ill, he might have come. 3.与将来事实可能相反
if从句：a.动词过去式（be一律用were） b.should+动词原形（不能用would） c.were to+动词原形
主句：would/could/might/should+动词原形 If he came tomorrow, I would tell him everything.
If it should rain tomorrow, I would stay at home and watch TV. If it were to snow tomorrow, they would not go out. Should he come tomorrow, please give the book to him. 4.错综时间条件句
在虚拟语气中，有时条件从句动作发生的时间和主句动作发生的时间是不一致的，称为错综时间条件句。这种句子的形式往往要根据句子的时间相调整，分别处理。
If you had spoken to him yesterday, you would know what to do now. If you had followed the doctor’s advice then, you would be all right now. If you had watered them more, the crops would be growing still better now. (有时时间会省略） 5.含蓄条件句
有时虚拟条件不用if条件从句，而用介词或介词短语来表示。 They would not be able to live without him.（如果没有） He would have failed but for his teacher’s timely advice. （要不是）=if it had not been for
If only you had worked with greater care!(要是......就好了） You would have done the same thing in her position.
With a little more care you could have avoid the traffic accident.
6.虚拟结合条件句
在虚拟语气中，假设的情况有时间可以通过上下文或其他方式表现出来，并且虚拟的情况和真实的情况同时存在。 I was ill that day. Otherwise, I would have taken part in the singing competition. （实------虚）
=I was ill that day. If I hadn’t been ill that day, I would have taken part in the singing competition. He would have bought the piano, but he didn’t have enough money.
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（虚------实）
=He would have bought the piano if he had had enough money, but in fact he didn’t have enough money. 7. 省略if倒装条件句
在虚拟语气中，if从句假设的情况中如果有助动词had, should和were，那么可省略if，把had, should和were放在句首构成倒装，简称省略if倒装条件句。
If he had finished the work yesterday, he would have gone to the concert with you.