The full meaning of Must

must

modal verb

 UK ​ strong /mʌst/ weak /məst/ /məs/ US ​strong /mʌst/ weak /məst/ /məs/

must modal verb (NECESSARY)

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A2 used to show that it is necessary or very important that something happens in the present or future:

Meat must be cooked thoroughly.

I must get some sleep.

You mustn't show this letter to anyone else.

Luggage must not be left unattended (= 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 look absolutely great.

I must admit, I wasn't looking forward 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 lunch soon.

More examples

• I must do some ironing tonight.
• Food must be heated to a high temperature to kill harmful bacteria.
• You must give the bank a written notification if you wish to close youraccount.
• Soldiers must obey orders.
• Candidates must answer two questions from each paper.

Thesaurus: synonyms and related words

must modal verb (PROBABLY)

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B2 used to show that something is very likely, probable, or certainto be true:

Harry's been driving all day - he must be tired.

There's no food left - 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."

More examples

Thesaurus: synonyms and related words

Grammar

Must…

Must: forms…

Must: uses…

Must and have (got) to?…

Must: typical errors…

must

noun [ C ]

 UK ​ strong /mʌst/ /məst/ /məs/ US ​ /mʌst/ /məst//məs/ informal

​

something that is necessary:

If you live in the country a car is a must.

Thesaurus: synonyms and related words

must-

prefix

 UK ​ /mʌst-/ 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 cashmere scarf is this season's must-have.

It's a moderately entertaining film but it's certainly not a must-see.

Thesaurus: synonyms and related words

(Definition of “must” from the Cambridge Advanced Learner's Dictionary & Thesaurus © Cambridge University Press)

"must" in American English

mustmodal verb

 US ​ /mʌst, məst/ must

must modal verb (BE NECESSARY)

​

used to show that it is necessary or important that somethinghappen 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 firm intention to do something in the future:

I must call my sister later.

​

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 betrue:

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)

Examples of “must”

These examples are from the Cambridge English Corpus and from sources on the web. Any opinions in the examples do not represent the opinion of the Cambridge Dictionary editors or of Cambridge University Press or its licensors.

You mustn't confuse the problem with the way in which the problem will be resolved.

From Cambridge English Corpus 

The top of the cooker mustn't look dirty, whatever happens.

From Cambridge English Corpus 

I mustn't prejudice my relationship with my minister beyond refusing to accept a ban on internal discussions within the department.

From Cambridge English Corpus 

I must've been really lucky to pass them.

From Cambridge English Corpus 

You mustn't, not with a complaint like he's got (wife, no diagnosis ; husband with dementia).

From Cambridge English Corpus 

We mustn't endorse technology for its own sake, nor simply for its economic potential, but ask what its ends are.

From Cambridge English Corpus 

In fact, one mustn't do it, not like that; one couldn't go on.

From Cambridge English Corpus