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Do Americans use "must" or "must not (mustn't)"?

hirashin

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8 Apr 2004
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Dear American English speakers,
do you ever use "must" or "must not (mustn't)"?

An American from another language forum says,
No one really says mustn't. Technically the sentence is correct but it's not current. We would say "don't open this box yet" or "you shouldn't open this box now"

Then I ask:
Oh, really? Thanks for the help、Jennifer.Is it that Americans never use "mustn't" or "must not"?

She answered:
We really don't use either. It's a bit old world. My grandfather might say it
("World" means "word, I think)

Hirashin
 
That's accurate.

Tho it's used in concluding that something might (not) have happened:

Nobody is answering the phone, he must be out walking the dog (or running errands).
They're late, they must not have left early enough, or they must have gotten caught in traffic.
 
Thanks, johnnyG. So you don't say something like "You must close the door when you leave the room".
 
Perfectly grammatical, but as your other person said, not used that way in the US for quite a while--I'd tag it as old-fashioned, stilted, perhaps also from a person with a little more education (the 'proper' way to talk/speak, more prescriptivist).

(You need/have to) Close the door when you leave the room.
Or similar sentence with "should" or "ought to".

I'm guessing, but you'd probably get a different POV from someone from UK, Oz, NZ.
 
do you ever use "must" or "must not (mustn't)"?
Never, but of course I still understand it.

It's a bit old world. My grandfather might say it
("World" means "word, I think)
I agree with her. Also, it's not a typo, although I think it's not quite correct usage.

"Old world" means Europe and Britain mostly, the opposite of "New world", the Americas. In contemporary usage it implies "the country my grandparents came from" or something similar. It's used almost only for things that are both old-fashioned and originated overseas, and honestly, is used mostly in marketing that wants to create a feeling of nostalgia and/or tradition.
 
Thanks, johnnyG and Chris.

"Old world" means Europe and Britain mostly, the opposite of "New world", the Americas. In contemporary usage it implies "the country my grandparents came from" or something similar. It's used almost only for things that are both old-fashioned and originated overseas, and honestly, is used mostly in marketing that wants to create a feeling of nostalgia and/or tradition.

Wow! I'm surprised to know that's not a typo. Thanks for the information.
I know the phrases "the Old World" and "the New World", but I didn't think of them when I read her comment.
 
Yeah, the adjectival use of 'old world' in modern English is a bit different from the use of 'the old/new world' in history books, so I wouldn't expect it to be immediately obvious. I don't think we Americans would even know what it means or use it if it weren't for commercials going on about 'old world style' and 'old world flavor'! (oh, and I don't know but I would lay high odds that it is exclusive to American and Canadian English.)
 
Must is mostly used today in it's predictive form, like, "There's a lot of traffic today, there must have been an accident."

Japan is pretty stubborn, and the curriculum is decided by old people who don't live in the West, so must is foundational in the curriculum here.

One of the posters above used the imperative "Don't" and "shouldn't" as alternatives, but I'd mention that Oxford texts at that level use "can't" instead, and simply don't teach must.
 
I think Americans do use must and must not but only in special and very, very serious circumstances, so yeah, not very much. British English speakers seem to use them more casually which to my American ears can cause a bit of alarm....like "You must not open this." and I am thinking, "What? Is it full of poisonous snakes?"

That said, I think Americans will also add a lot of other words any time they used something like "must not". Such as "You must not, under any circumstances, ever push this button. Do you understand?"

However there is another more common use in American English (and probably British as well), and that is when you are saying something is very unlikely. For example, you see that your friend lost weight and not in a good way, and you say to someone "He must not be eating much."

Edit: "Have to" is more commonly used in place of "must". For example: "You look like you are going to die! You have to go to a hospital right now!" Someone could even say "must" in such a case and it would not be strange, but it would be less common.
 
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