条件句共有四个，其翻译和改写情况如下：
一、真实条件句，例如：
如果我有空，我就去。
If I am free, I will go there.
如果天气好，我就去。
If it’s fine, I’ll go there
二、对现在提出相反的价值，现在的结果，例如：
如果我是你的话，我就去。
If I were you, I would go there.
如果他在这儿的话，他会很高兴。
If he were here, he would be happy.
以上英文句子里的If可以省略，那么两个句子就可以分别写成：
Were I you, I would go there.
Were he here, he would be happy.
三、对过去提出相反的假设，过去的结果，例如：
如果你来得早一点，你就会见到王勇了。
If you had come earlier, you would have met Wang Yong.
以上英文句子里的If可以省略，那么这个句子就可以写成：
Had you come earlier, you would have met Wang Yong.
四、对过去提出相反的假设，现在或将来的结果，例如：
如果当初我读了大学，我现在就是经理了。
If I had gone to university, I would be a manager now.
以上英文句子里的If可以省略，那么这个句子就可以写成：
Had I gone to university, I would be a manager now.
注意：在以上四个条件句中，后三个条件句是虚拟语气。
（方开瑞）