must Meaning in the Cambridge English Dictionary
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Meaning of “must” in the English Dictionary

"must" in British English

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mustmodal verb

uk   us   strong /mʌst/ weak /məst/ /məs/

must modal verb (NECESSARY)

A2 used to show that it is ​necessary or very ​important that something ​happens in the ​present or ​future: Meat must be ​cookedthoroughly. I must get some ​sleep. You mustn't show this ​letter to anyone ​else. Luggage must not be ​leftunattended (= it is against the ​rules).formal Must you ​leave so ​soon?formal "Must I ​sign this?" "Yes, you must." If you say that you must do something, you ​mean that you ​stronglyintend to do something in the ​future: I must ​phone my ​sister. We must get someone to ​fix that ​wheel.UK I mustn't ​bite my ​nails. used for ​emphasis: I must say, you ​lookabsolutelygreat. I must admit, I wasn't ​lookingforward to it.B1 If you ​tell someone ​else that they must do something ​pleasant, you are ​emphasizing that you ​think it is a good ​idea to do that: You must come and ​stay with us one ​weekend. We must ​meet for ​lunchsoon.
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must modal verb (PROBABLY)

B2 used to show that something is very ​likely, ​probable, or ​certain to be ​true: Harry's been ​driving all ​day - he must be ​tired. There's no ​foodleft - we must have ​eaten it all. When you got ​lost in the ​forest you must have been very ​frightened. "You must ​know Frank." "No, I don't."
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mustnoun [C]

uk   us   strong /mʌst/ weak /məst/ /məs/ informal
something that is ​necessary: If you ​live in the ​country a ​car is a must.

must-prefix

uk   us   /mʌst-/ informal
a must-do, must-have, must-see, etc. something that is so good, you must do it, have it, or ​see it: The ​cashmerescarf is this season's ​must-have. It's a ​moderatelyentertainingfilm but it's ​certainly not a must-see.
(Definition of must from the Cambridge Advanced Learner’s Dictionary & Thesaurus © Cambridge University Press)

"must" in American English

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mustmodal verb

 us   /mʌst, məst/ (must)

must modal verb (BE NECESSARY)

used to show that it is ​necessary or ​important that something ​happen in the ​present or ​future: Seeing what ​others have and she ​lacks, she ​believes that she must have more. We must not ​surprise them (= it is ​wrong, ​dangerous, or ​forbidden). If you say that you must do something, you can ​mean that you have a ​firmintention to do something in the ​future: I must ​call my ​sisterlater. Must is sometimes used for ​emphasis: I must ​admit I ​enjoy these ​movies.

must modal verb (PROBABLY)

used to show that something is ​likely, ​probable, or ​certain to be ​true: Death must be ​better than this. "It must have been ​fun." "No, it wasn’t."

mustnoun [C]

 us   /mʌst/
something that is ​necessary: If you ​live in the ​suburbs a ​car is a must.
(Definition of must from the Cambridge Academic Content Dictionary © Cambridge University Press)
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