Usage and Grammar

Q. I would like to know more about the use of the modals can and may. Here in Brazil it is being taught that both can be used, as in “Can/May I erase the board?” Could you please distinguish both for me?

A. Traditionally, “Can I?” means “Am I able to?” whereas “May I?” means “Do I have permission to”?

Can I lift six times my weight? Can I get to the parking lot through this alley?

May I take your plate? May I go ahead of you in line?

This use of may is dying, however. We tend to hear it from grandparents when a child asks “Can I have some candy?” and the grandparent replies “May I!” Although it’s not rude to use can when you are asking permission, it is incorrect to use may when asking whether something is possible.