1在请求时,没区别
如 Could you go with me?=Would you go with me?
2在表示习性时,不用could ,用 would
Ipushed the door,but it wouldn't open.
我用力推门却推不开．
3could用在wish的句型中：
I wish I could go to the Moon.
4 would ,could 都可以用在带if条件句的虚拟语气主句中,意思大致不变．
If I had a lot of money,I would/could buy a set of house in Beijing.
5 表示推测时,不用would
She could have gone to the cinema .(她可能看电影去了）