could和can都是情态动词，后面接动词原形，can do something表示现在的能力，could do something表示过去的能力。情态动词表语气，can表示一种自己非常强的自信的语气，could表示一种悔恨遗憾的语气。
扩展资料
could的例句：
I could come next week, or the week after.
我可能下周来，或者再下一周。
The operation could prolong his life by two or three years.
这次手术可使他多活两三年。
Events could have developed in a dramatically different way.
事情本来可以发展成另一种样子。
