Tonight I had dinner with one of my Japanese friends and he suggested I write about the difference between the words “can you”, “could you” and “would you”. So that is what I’m going to do.
In terms of formality, “can you” is the most casual, “could you” is more polite and “would you” is the most formal and polite. There is no major difference in meaning between “can you” and “could you” except that “could you” is more polite. However, there is a difference in nuance between “could you” and “would you”. The words “could you” focus on the ability to do something, but the words “would you” focus on the willingness to do something. For example:
Can you help me with my homework later? (said to a friend or family member)
Could you tell me how to get to the train station from here? (said to a stranger on the street)
Would you lend me your car this weekend? (said to a friend or family member, but in a very polite way because you want something from them)
Sometimes people get confused between the difference between “could you” and “would you” but there is one example sentence which usually helps people to understand. If a man is asking someone to marry him, he would say:
Would you marry me?
But he would NEVER say:
Could you marry me?
By saying, “Would you marry me?” he is asking “Are you willing to marry me?” but if he said “Could you marry me?” it sounds like “Do you have the ability to marry me?” (which sounds quite strange and VERY unromantic.) Here are some other examples for you to study:
Can you drive me to work today? My car isn’t working now.
Could you tell me how long I’ll have to wait until I can see the doctor?
Would you please stop tapping your foot? I’m trying to study.
So I hope this helps people to understand the difference between these words.