He may not/need not wake up early because it is Sunday.

How can we decide that only one is the right answer that's why I put this sentence?

  • 3
    Please, don't use the imperative on us. We aren't your slaves after all. – SovereignSun Dec 5 '17 at 11:55
  • 1
    may not: his decision, needs not: other's decision that may or may not influence the time he decides to get up – mplungjan Dec 5 '17 at 12:25

According to Oxford Dictionaries, may "expresses possibility". Hence, "may not" means that there is a possibility that he will not wake up early (presumably, it is up to him whether he does or not)

On the other hand, need means "to require". So "need not" means that he is not required to wake up early (someone else's decision).


He may not...: He is not allowed to; it is forbidden (This can also mean "It is possible that he will not" or "He might not"; but the word "may" is most often applied to actions like "waking up early" in the sense of giving (or revoking) permission).

He need not...: He does not need to; he is not required to (in this sense, it is the opposite of "He must..." or "He needs to").

Assuming we use the more frequent, permission-revoking sense of "may not," this gives us two options:

He is not allowed to wake up early, because it is Sunday. (Unlikely, unless there's a cultural reason which I don't know about which forbids people from waking up early on Sunday).

He does not have to wake up early, because it is Sunday (This is more likely; in most English-speaking countries, Sunday is a day of rest, an idea which comes from Christianity. He probably does not need to want up early, because he probably does not have to work on a Sunday)

Altogether, the second option ("He need not...") seems more correct in context.

  • "incorrect colloquial meaning" - this is not true in British English at least. Oxford Dictionary, Cambridge Dictionary and Collins Dictionary all give the "possibility" meaning as the primary definition with no mention of it being "colloquial". – D. Nelson Dec 5 '17 at 13:10
  • @D.Nelson I read the OED's description, especially the examples, of the "expressing possibility" meaning as referring to outcomes or states (from the online OED, "winning" and something "being true"), whereas the "granting permission" meaning is the one more correctly applied to actions or courses of action (ib. "confirm my identity" and "ask questions"). That's the way I way I was taught, as well - we speak mostly British English here as well. But I'll edit the answer to correct it, as you're correct and it's not colloquial in many situations. – Watercleave Dec 5 '17 at 13:25

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