Can or May?

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Can or May?

What is the difference between "can" and "may"?

In a polite or formal setting, use "may" for permission. For example:
  • May she swim in your pool?
    • (This means "Is she permitted to swim in your pool?" It sounds polite.)
In an informal setting, it is okay to use "can" for permission. For example:
  • Can she swim in your pool?
    • (This means the same as the one above. It sounds neutral as opposed to polite.)
Use "can" for ability. For example:
  • Can she swim?
    • (Is she able to swim?)
  • Can she do quadratic equations?
    • (Is she able to do quadratic equations? You cannot use "may" to express ability.)
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More about "Can"

The word "can" is an auxiliary verb used to express ability. For example:
  • I can whistle.
    • (I have the ability to whistle.)
  • Can he lift 150 kgs?
    • (Does he have the ability to lift 150 kgs?)
"Can" can also be used to express permission. For example:
  • You can stroke the ponies but not goats.
    • (Here, "can" expresses permission. "Can" tends to be used for permission among friends or in an informal setting.)

More about "May"

The word "may" is an auxiliary verb used to denote permission. For example:
  • You can swim in this river.
    • (You are allowed to swim in this river.)
  • May I have a biscuit?
    • (Am I permitted to have a biscuit?)
If you have a reason to be "über correct" (e.g., you're hosting royalty or a very pedantic grandparent), you should use "may" and not "can" to express permission. It is true to say that "may" and "can" are becoming interchangeable to express permission.

A Quick Joke

This joke plays on the idea that "can" and "may" were not always interchangeable to express permission:

can or may?
Interactive Exercise
Here are three randomly selected questions from a larger exercise, which can be edited, printed to create an exercise worksheet, or sent via email to friends or students.

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See Also

cannot or can not? adverse or averse? affect or effect? appraise or apprise? avenge or revenge? bare or bear? complement or compliment? dependant or dependent? discreet or discrete? disinterested or uninterested? e.g. or i.e.? envy or jealousy? imply or infer? its or it's? material or materiel? may and might poisonous or venomous? practice or practise? principal or principle? shall and will cannot or can not? who's or whose? What are auxiliary verbs? What are verbs? List of easily confused words