So what is the difference between "you have to do this" and "you must do this"? Don't they mean the same?

Same goes with "he may be in the library" and "he might be in the library". I'm kind of confused on which one to use in above's context.

  • For future questions, please post things like this as two separate questions. That way answerers can focus on each separately.
    – saritonin
    Commented Nov 14, 2022 at 7:47
  • Does this answer your question? "May" & "Might": What's the right context?
    – saritonin
    Commented Nov 14, 2022 at 7:50
  • @saritonin That doesn't seem to be asking the same thing as this question. Commented Nov 14, 2022 at 9:30
  • @Randal'Thor english.stackexchange.com/questions/304263/… is closer for the first question. But the link I posted does ask the second question and the answers discuss this asker's nuance in detail.
    – saritonin
    Commented Nov 14, 2022 at 9:51

1 Answer 1


While the terms are indeed quite similar in meaning, they have different connotations (feelings).

Saying have to seems less required than must because must tends to be used more in formal settings.

In your example, may and might are also quite close in meaning. They do express slightly different degrees of certainty, though. May generally indicates a higher likelihood than might. If "he may be in the library," that could probably be a good place to start looking for him. If "he might be in the library," that implies you're more unsure about his whereabouts.

This article from Masterclass (warning: video autoplay on that site) explains might vs. may pretty well. https://www.masterclass.com/articles/may-vs-might-explained

It also clarifies the important distinction that may is used to indicate permission as well as probability. "May I have a moment of your time?" is the much more common way to ask permission in American English, at least. If I hear, "Might I have a moment of your time?" it feels more stuffy and formal or more British to my American ears.

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