第二条件句

我们会用第二条件句来表示现在或未来的假设或不真实的情况。

If I won the lottery, I would buy a yacht. 如果我中了彩票，我会买一艘游艇。
If I had a better salary, I could travel more. 如果我有更好的薪水，我可以旅行更多。
If I were you, I might wait before making a decision. 如果我是你，我可能在做决定前等待下。
If it weren’t for his help, I might be dead now. 如果不是他的帮助，我现在可能已经死了。

第二条件句的用法

If 从句和主要从句

我们用 if + 过去式，来表示一种假想中的现在或未来的状况(虽然动词是过去式，但时间是表示现在或未来)。而我们用 would + 不定词来表示这个假想情况的结果。

If I had a swimming pool in my yard, I’d go every day. 如果我的院子里有一个游泳池，我会每天都去。
Would you call him if you got his phone number? 如果你知道他的电话号码，你会打电话给他吗？

加逗号

当 if 从句在前面的时候，我们通常会在 if 从句后面加个逗号；当主要从句在前面、if 从句在后面的时候，我们通常不加逗号。

如果你来参加聚会，你会跳很多舞。
If you came to the party, you’d dance a lot.
You’d dance a lot if you came to the party.

句中 would 的用法

would/wouldn’t 在所有的人称中都是一样的用法。

I/you/he/she/it/we/they would/wouldn’t do that if it was possible. 

缩写的方式: wouldn’t= would not，‘d= would

I’d never pass my test if you failed to bring my books. 如果你不带我的书，我永远不会通过我的考试。
I wouldn’t pass my test if you failed to bring my books. 如果你不带我的书，我就不会通过考试。

句中 could 的用法

在主要从句中，我们通常可以用 could + 不定词，来代替 would +不定词。

If you wrote the book, you could give me a sign. 如果你写这本书，你可以给我一个签名。

要用 was 或 were?

在第二条件句中，我们可以用 if I/he/she/it were（较为正式）来代替 if I/he/she/it was。

If he were/was a good singer, he would win the contest. 如果他是/是一个好歌手，他会赢得比赛。

但是当我们用 if I were you这样的句型来表示给予某人建议时，我们用 were（请注意，不是 was）。

If I were you, I would break up with him.
I wouldn’t go to that restaurant if I were you.

第一条件句 VS 第二条件句

我们用第一条件句来表示可能的未来状况，而用第二条件句来表示假设性或假想中的未来状况。

如果下午晚些时候我没有预约医生，我一定和你一起去购物。

If I don’t have a doctor’s appointment later in the afternoon, I’ll have to go shopping with you. (这是有可能的，也许我明天没有和医生挂到号，所以可以和你一起去逛街。)

If I didn’t have a doctor’s appointment later in the afternoon, I’d have shopped with you. (这是假设性的，因为我明天已经向医生挂号了，所以不可能和你一起去逛街。)

第二条件句 – 练习题