I bet most of you can think of a time when you’ve been corrected on your use of the word “can” – probably by an older adult when you were a child, and probably with a fair amount of bossiness or snark.

“Can I have some ice cream?”
“May you have some ice cream?”

“Can I go outside?”
“Yes, you may go outside.”

Or my favourite, which I will attribute to a teacher at my high school (let’s call her “Mrs. so fascist, though”) who I did not have the dubious pleasure of studying under, though many of my friends did:

“Can I go to the bathroom?”

“I don’t know, can you?”

Confusing these two words seems to be something that many children and young adults do, but the moment they turn thirty, they suddenly remember to use the word “may” instead of “can” when asking for permission to do something, and not-so-gently reminding their own kids to do so. (And correcting the kid behind the counter at McDonald’s who asks if they “can help who’s next.” Don’t even get me started on that sentence construction – that’s a whole other blog post).

The thing is, I’m not sure everyone knows the reasoning behind when it’s correct to use “may.” Some people seem to think that it’s somehow more polite or refined than “can,” when in fact the two words have totally different meanings.

So let’s get it settled once and for all: In English it is correct and precise to use the word “may” in all situations where you are asking for permission or determining whether something is possible. To wit:

• May I be excused?
• May I help you find something?
• May I have another piece of cake?
• May my daughter please have a turn on the swings now?

However, we use “can” to determine or demonstrate ability.

• I can run really fast.
• She can fly an airplane.
• He can eat fifteen hot dogs at one sitting!
• Can you see out that window?

The easiest way to quickly tell which word you want is to remember that “may” begins with m, and the word “permission” also has an m in it. If you’re not asking for permission to do or have something, it’s usually safe to use “can.”

In the service of clarity, it’s always a good idea to use the most precise word if you can. But remember that correcting someone else may backfire on you if they catch you doing it as well. It’s such a common error that I guarantee you and I and everyone we know has done it at least once, and it may happen again when you least expect it. What can you do? Such is life.