Can vs. May--Not So Simple!

The correct places to use the words can and may are not as easily determined as we often imagine. I was reminded of the subtleties in my seminar with the Association of Legal Administrators last week, when an attendee questioned two of my uses. (Thanks, Jennifer! I appreciate your commitment to correctness.)

Here are the simple rules:

Can is for ability:
"Can you drive a car with a standard shift?"

May is for permission or possibility: 
"You may borrow my car next week." (Permission)
"I may arrive late." (Possibility)

But using the simple rules above, the choice between can and may may not be obvious in the sentences below. Which word would you choose?

1. Can/May I have food served in the conference room?
2. Yes, you can/may make arrangements with the onsite cafe.
3. Professional guests can/may have their parking tickets validated.
4. Please leave your phone number so that I can/may call you back.
5. Please approve these specifications so we can/may process your order.
6. You can/may review 440 lessons in the archives.

For the sentences above, does the meaning involve ability, possibility, or permission?

I would say each one involves ability. For example:

1. Am I able to have food served in the conference room?
2. Yes, you are able to make arrangements with the onsite cafe.
3. Professional guests are able to have their parking tickets validated.

I do not see the sentences as communicating permission, but another person might view them that way:

1. Am I permitted to have food served in the conference room?
2. Yes, you are permitted to make arrangements with the onsite cafe.
3. Professional guests are permitted to have their parking tickets validated.

My objection to may is that it may (possibility) be misunderstood. Do the sentences below indicate possibility or permission?

Professional guests may have their parking tickets validated.

Repeat visitors may receive a special discount.

I advise this approach:

If you intend "able to," use can.
If you mean "will possibly," use may.
If you intend "permitted to," use may.

I believe this approach will make the choice clear in nearly all instances, but I may be wrong. That is, I will possibly be wrong, and I am permitted to be wrong--sometimes. I certainly know I can be!

Lynn

Comments

[Aaron Nelson]

Hi Lynn,
This is great stuff! You likely can appreciate how tricky our language can be in that you get into trying to explain it to others during your workshops. Can and May are very common problem creators with my English students, and it's usually a monster to try and explain. I liked your explanation, and I'll be saving it to maybe make things easier on my students.

One thing is explaining to a native english speaker, another thing is trying to do it with folks who are trying to learn it as a second language...the whole dynamic changes. Your post will be a very useful tool - thanks!

Aaron in Mexico City

[Lynn]

Aaron, I always like to hear your reactions and challenges. Let me know if you want me to write about any particular topics.

[Caen]

I'm so glad I happened across this post with the Google-search, "can vs. may"! Now that I grasp it, I'm sure I *can* use each properly; I *may* even be able to explain it to others! *May* I link to this post as a reference?

[Lynn]

Caen, thanks for the comment. Yes, you may link--if you can!

[Lisa]

looks like you're right

[Alessio]

lol i'm trying to write an university essay on that ... :D

[GM]

Thanks for the explanation. I have a 16 year old Godson that insists it's "may you pass me the ketchup" and his cousin who says "may you give me the money to buy my own clothes". Both are incorrect are they not?

[Lynn Gaertner-Johnston]

"May you" is incorrect. Please see my post "Show Me the Manual." (Insert that title in the Google search box, and you will find the post.)

Lynn

[jamesBA]

Very informative.