Can or May - Which is Correct?

Modals (perhaps you learned them in school as a kind of auxiliary or "helping" verbs) are among the most confusing English words to master. And no wonder: also their refusal to follow the patterns verbs usually take, we also use some of them interchangeably so usually that we forget they are not same in meaning. Can and may are two of the English modals that have fallen into that pattern.

The basic inequity between can and may is pretty simple. Can is about ability; may is about permission*. Think these two examples:
John is a piano prodigy who can flawlessly recreate a full concerto after hearing it only once.
John may play the piano after he finishes the liver-and-onion casserole his mom made for dinner.

Piano Concerto

In the first sentence, the focus is on John's broad capability: he Can. In the second, John's potential to play is beside the point; under what condition he is allowed to practice his talent is the question: he May.

When you're not sure which to use, jog your memory by thinking of these two celebrated instances.

Sammy Davis, Jr.'s song "Yes I Can" = Ability

vs.

the children's game "Mother, May I?" = Permission

Try distinguishing the inequity with a few example sentences. Perfect each one with either can or may.

1) A talented chef ___ put in order a delicious cake without using any dairy, egg, or wheat products.

2) ___ I borrow your car while you are on vacation?

3) Passengers ___ not walk nearby the cabin while the "Fasten Seatbelts" sign is on.

4) If he takes a running start, Phil ___ accomplish a long jump of over twelve feet.

5) The boss knows Wilma ___ do the job; it requires the skills Wilma demonstrated in her old position.

Answers: Sentences 1, 4, and 5 need can; may completes 2 and 3.

English speakers are often guilty of using can in both instances. In daily speech, chances are most population wouldn't even consideration the substitution. The Chicago by hand of Style (15th Edition) acknowledges that, in informal situations, can is often used to indicate permission in the same way may is above. However, Chicago also offers a caveat: in any kind of formal writing, may to express permission is far preferable to can. Likewise, in a speaking situation other than casual conversation, it would be prudent to consciously use the correct modal.

*May has a second usage as well: an expression of possibility. (Ex: If conditions are right, I may go fishing this weekend.) However, that usage is more ordinarily confused with might than with can--a question which will be addressed separately in a hereafter article.

Can or May - Which is Correct?

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