This is a good question, and the words are often not used correctly. "May" I help you? "May I go to the store? This is asking permission to do something. "Yes, you may" is the right response, or "no, someone else is helping me, or no, you have to eat now, so you may not go to the store yet". "Can" I help you? This actually means am I able to help you. The answer could be, "no you can't help me because you don't have what I need, I'll have to go to a different store. "Can" I go to the store? No, you can't, because you don't have a driver's license, and it's too far to walk. You are not able to go. We often hear "Can" used instead of "may", and it's so common, we don't correct anyone about it, but technically they mean different things...asking permission or having the ability to do something.

Well, the native speakers who are telling you that it is wrong to use "can" to ask for permission should probably tape record what they say for a few days. The results might be surprising! We all use "can" to ask for permission, even in formal contexts. And I don't just mean that we sometimes use "can" this way. Research shows that native speakers actually use "can" to ask for permission far more often than "may." I still remember my school days, when a child would ask, "Can I go to the bathroom?" and the teacher, who very literally might have been born in the 19th century, would light up with this smug mixture of triumph and outrage and sarcastically reply to the child, "I don't know. CAN YOU?!?" Ugh. Of course, the next time you have tea with the Queen of England you should remember to use "may" to ask for permission. Otherwise, "can" will do just fine and will sound a lot more natural.

May is much more polite and respectful.

may= do i have the permission to May I help you? = Do I have the permission to help you? can = am I able to Can I score high in maths? = Am I able to score high in maths? hope this helps. :)

Thank you very much for your answers. Now I understand.