can't/mustn't [prohibition]

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angelene001

Senior Member
Polish
I have to be on time at work this morning.
I ............. be late for work this morning.
a) mustn't
b) can't

Are both possible?
I would probably choose "can't" because it sounds better to me.
 
  • perpend

    Banned
    American English
    I would use both a) and b) in American English, in my dialect (Midwestern American English.)
     

    suzi br

    Senior Member
    English / England
    Hi
    I think it would be OK with either option although I think "mustn't" seems slightly more suitable, expecially if there is an external pressure on me about the time keeping.
     

    velisarius

    Senior Member
    British English (Sussex)
    Like suzi, I would go for "must" as a more exact synonym.

    For me, "I have to be on time /I mustn't be late" mean exactly the same. "I can't be late for work this morning" is also possible, but sounds to me less urgent than "must not", and I personally wouldn't use "can't if I meant "mustn't".
     

    angelene001

    Senior Member
    Polish
    I try to understand the difference between can't and mustn't when used to express a prohibition.

    I've found this in a grammar book:


    You can't eat sandwiches in the library = 1) I don't allow it


    2) The librarian doesn't allow it


    3) It isn't the proper thing to do




    What would a sentence with mustn't mean?
    This is how I understand it:
    You mustn't eat sandwiches in the library
    = 1)notice on the wall in the library
    2) strong advice given to somebody --> You mustn't do this because if the librarian catches you at eating, he will tell you off.
    3) to report a rule to someone; for example I'm telling a friend what rules he needs to obey in the library.


    Would you add something to the both lists?
    Are there any other ways in which these sentences may be understood?
     

    Chrzaszcz Saproksyliczny

    Member
    Polish - Poland
    Can't - is used for more things, including lack of possibility, lack of skills to do something, misbelief - "That can't be Jeremy Corbin!".
    Musn't - is for prohibitions only. I'd say it's stronger than can't, and more authoritative.
     

    Sparky Malarky

    Moderator
    English - US
    Can't - is used for more things, including lack of possibility, lack of skills to do something, misbelief - "That can't be Jeremy Corbin!".
    Musn't - is for prohibitions only. I'd say it's stronger than can't, and more authoritative.
    This is true, but we hardly ever use "mustn't." Perhaps it's used more in BE (I honestly don't know) but it sounds antiquated and almost childish.

    However, using only can't leaves room for misunderstanding, though the meaning is usually clear from context.

    I can't drive my car into the library. Because it would cause property damage - doing so is against the law.
    I can't lift my car. Because it is too heavy - lifting it is impossible.

    I can't park my car there. Why? Because it is prohibited? Because my car won't fit?
     

    angelene001

    Senior Member
    Polish
    What about paraphrasing such a sentence:
    You aren't allowed to eat and drink in the classrooms.

    It's taken from a grammar exercise and it's out of context.

    Are both can't and mustn't correct?
    You can't/mustn't eat and drink in the classrooms.
     

    Einstein

    Senior Member
    UK, English
    "You mustn't smoke in the library" sounds like the librarian's personal opinion. I agree with Sparky Malaky that it doesn't sound right for an official statement.

    You aren't allowed to eat and drink in the classrooms. OK
    You can't eat and drink in the classrooms. OK
    You mustn't eat and drink in the classrooms. NO

     

    panjandrum

    Lapsed Moderator
    English-Ireland (top end)
    My understanding is opposite to Einstein's (bad day to be confessing that).

    As I understand it, I can eat and drink in the classrooms. Such action may result in serious punishment, but nevertheless, it is possible, so it cannot be correct to say 'You can't eat and drink in the classrooms.'
    It would be correct to say 'You mustn't eat and drink in the classrooms.' That tells me that although such actions are possible, they are not permitted, not advisable.
     

    Sparky Malarky

    Moderator
    English - US
    I agree that "You mustn't eat in the classrooms" is grammatically correct, but I also agree that it is not idiomatic. It sounds as though you're instructing a small child.
     
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