Can and May

The Quick Answer
What is the difference between can and may?

Use may for permission. For example:
  • May she swim?
    • (Is she permitted to swim?)
Use can for ability. For example:
  • Can she swim?
    • (Is she able to swim?)
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Can and May

There is often confusion over the words can and may.

Can

The word can is used to denote 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?)

May

The word may is used to denote permission. For example:
  • You may swim in this river.
    • (You are allowed to swim in this river.)
  • May I have a biscuit?
    • (Am I permitted to have a biscuit?)

Can for Permission (Informal Setting)

These days, the word can is used for both ability and permission, particularly in an informal setting. For example:
  • You can swim in this river.
    • (You are allowed to swim in this river.)
  • Can I have a biscuit?
    • (Am I permitted to have a biscuit?)

Use May for Permission in a Formal Setting

If you have a reason to be "uber correct" (e.g., you're hosting royalty or a very pedantic grandparent), you should use may to denote permission. For example:
  • May I leave the table?
    • (Am I permitted to leave the table?)
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See Also

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 tenant or tenet? who's or whose?
What are auxiliary verbs? What are verbs? List of easily confused words