May and can are used to indicate that something is allowed, but "may" is more formal: "You may leave whenever you like" is more formal than "You can go whenever you want to. You have probably been taught that only "may" is used for permission, and that "can" is used only for ability. (For example, a child may ask a question like "Can I go outside?" and the responding adult might correct the child by saying that the child is able to go outside, but must ask permission by using "may.") "Can," however, is often used for permission. "Can," "may," and "could" are all used to make requests. "May" is formal in these contexts, while "can" and "could" appear mainly in speech: "May I have your attention?" is more formal than "Can I have your attention?" or "Could I have your attention?" Greetings