should, would, could 要用哪一个?

should, would, could 词形相近，用法不同

should 用法

“should” 通常用来“给建议”，比如：

That dress looks great on you. I think you should buy it.

这件裙子很合适你，我觉得你应该把它买下来。  

could 用法

“could”的用法大概可归纳为三种：

1) 描述过去的能力，比如：

 When I was young, I could jump over the fence.

当我小的时候，能跳过篱笆。

2) 描述未来的可能性，比如：

If we try to master English, I think we could travel around the world.

如果我们努力精通英语，未来可能会去环游世界。

3) 表达礼貌的请求，比如：

  Could I have a cup of coffee ?

我可以来杯咖啡吗？

would 用法

“Would” 的用法通常分为两类：

1）描述不可能或不真实的情况，比如：

 He would go to school like us if her parents were alive.

如果他的父母还活着，他就会跟我们一样去上学。 （他的父母已经不在了。）

2）表示礼貌的提供帮助，比如：

 Would you like some tea?

您要喝点茶吗？