Can vs. May
Although, traditionally, can has meant “to be able” and may has meant “to be permitted” or to express possibility, both can and may are commonly used interchangeably in respect to permission.
Example: He can hold his breath for 30 seconds.
Meaning: He is able to hold his breath for 30 seconds.
Example: He may hold his breath for 30 seconds.
Meaning #1: It is possible that he will hold his breath.
Meaning #2: He has permission to hold his breath. (This meaning is unlikely.)
Example: May/Can I go to the mall tonight?
Regardless of whether you choose can or may here, it is clear that permission is being requested.
In spoken English, a request for permission is generally answered with can, cannot, or can’t, rather than with may or may not, even if the question was formed using may. (Although mayn’t is a word, it looks and sounds strange even to native speakers.)
Example of Dialogue:
“May I go to the mall tonight?”
“No, you can’t/cannot go.” OR “Yes, you can go.”
Occasionally, you may hear someone say something like, “I cannot but argue when you say such silly things.” The expression cannot but is actually a shorthand way of saying “cannot help but.” You may also hear the expression can but, which means “can only.”
Example: We can but do our best to arrive on time.
Pop Quiz
1. Can/May you imagine a world without war?
2. Can/May I call you for a date?
3. She can/may run faster than anyone else on the team. (able to)
Quiz Answers
1. Can
2. Can or May
3. Can


February 27, 2007 at 9:45 pm
I am very happy to see that you make a distinction between may and can. I teach ESL students at the elementary and college levels. I had talked to the ” Grammar Lady ” a few years ago. She said that the rule had been relaxed and you could use can for permission. I refused to accept that and continued to teach the difference between the two. I had two elementary school teachers who taught grammar with a passion. I loved learning about grammar
and diagramming. I have found only two other people who feel the way I do about grammar. Thank you for the service you provide.
Larry E. Henry
February 28, 2007 at 12:06 am
Larry, you are most welcome.
March 18, 2007 at 4:15 am
Larry/Jane: I too am pretty passionate about grammar.
March 26, 2007 at 3:02 am
Now which one is more appropriate:
1. “May I speak to ….”
2. “May I speak with…”
3. “Can I speak to…”
4. “Can I speak with…”
5. “Could I speak with/to…”
March 26, 2007 at 2:03 pm
“May I speak to…” and “May I speak with…” are both correct. “Can” is used for ability while “may” is used for permission, which fits with your example.
March 29, 2007 at 6:42 am
Thank you Jane. It’s crystal clear to me now.
March 30, 2007 at 6:28 pm
http://www.bartleby.com/61/76/C0057600.html
Generations of grammarians and teachers have insisted that can should be used only to express the capacity to do something, and that may must be used to express permission. But children do not use can to ask permission out of a desire to be stubbornly perverse. They have learned it as an idiomatic expression from adults: After you clean your room, you can go outside and play. As part of the spoken language, this use of can is perfectly acceptable. This is especially true for negative questions, such as Can’t I have the car tonight? probably because using mayn’t instead of can’t sounds unnatural.
March 30, 2007 at 9:15 pm
It’s true that spoken language is often different from written language. Your examples with “can” and “may” are good ones.
March 27, 2008 at 6:26 pm
When my children ask, “May I go outside?” Do I response “Yes, you can.”?
March 29, 2008 at 3:53 pm
I’m sure that a simple “yes” is enough for them to go running out the door. However, I won’t sidestep your question. To help them understand the distinction between “can” and “may,” you may wish to say, “Yes, you may.”
May 7, 2008 at 6:26 pm
Grammar lovers tend to love rules. Alas, grammar is often not nearly as cut-and-dried as these folks would like. Merriam addresses far more than the stark permission / ability dichotomy. In many contexts “can” and “may” are interchangable. “May” certainly may (sic) be used to denote possibility. Hence, the procedure “You may click the third link to open the PDF” is fine, despite all those that scream can! can! until the woman with the ruffled dress starts dancing with a high kick.
April 7, 2009 at 12:58 pm
i have a colleague who, in emails, types, “may you (call this person, meet me at 3pm, etc.)” instead of, “can you”. it drives me crazy, because i know it’s not correct, but i don’t know how to tell her. could you give me the rule?
thanks!
April 7, 2009 at 2:55 pm
“Can you” would be correct because these questions imply the ability to fulfill the request, not permission to do so. Example: You can eat cake. (You have the ability to eat cake.) You may eat cake. (You have permission to eat cake.)
June 10, 2010 at 9:57 pm
Lol.
Wow! I’ve always wondered about this; I’ve recently started to use “may” a lot more (at the appropriate time of course). But, “can” seems, to me, to be more used informally used to mean can/may and “may” used formally to mean can/may. But that’s just me.
It doesn’t help though that other people still use “can” anyway to mean can/may.
Whenever my baby sister gets the chance to come around to my house, I insist on her using “May I?” whenever she wants something, hehe.
Good AND correct expression seems to be a priceless skill that many still need to acquire.
Good job Jane
June 11, 2010 at 2:58 pm
Thanks for the compliment. You bring up a good point about “can” being used in place of “may” in informal writing. English is a living language; therefore, rules become outdated and vocabulary changes constantly. Thanks for writing.
June 15, 2010 at 5:36 pm
Is it correct to answer a phone call with “How can I direct your call?” Or, is the only proper way “How may I direct your call?”
June 16, 2010 at 3:12 pm
The word “may” is used for permission and “can” is used for ability. Therefore, “How may I direct your call,” would be correct.