There are 4 main definitions of must in English:

must1

Syllabification: must
Pronunciation: /məst
 
/

verb (past had to or in reported speech must)

1Be obliged to; should (expressing necessity): you must show your ID card it must not be over 2,000 words she said she must be going
More example sentences
  • Their culture and way of life must of necessity reflect a human-centred moral order.
  • This is a necessity and you must start doing it now because it is an exam technique.
  • Obviously, the central biographical facts in all of these volumes must necessarily be identical.
Synonyms
ought to, should, have (got) to, need to, be obliged to, be required to, be compelled to
1.1Expressing insistence: you must try some of this fish if you must smoke, you could at least go in the living room
More example sentences
  • If you must smoke then smoke at home, mess up your own house, keep your own rubbish and leave the rest of us smoke free.
  • If someone must smoke on the road, stop at a rest stop for a smoke break outside the car.
  • There's a lot to be said for due process - but in this case we must insist as a country that the rules can sometimes be wrong.
1.2Used in ironic questions expressing irritation: must you look so utterly suburban?
More example sentences
  • The risks have been proven so why must non-smokers still be subjected to smoke they don't want to inhale?
  • If they cannot spit when they're smoking inside a restaurant, why must they do it outside?
2Expressing an opinion about something that is logically very likely: there must be something wrong you must be tired
More example sentences
  • The likely rationale must be that the company sees the fixed line telecom business as a potential cash generator.
  • So, we must logically have some control over which management tools we use.
  • While they all use the same delivery mechanism it is likely that prices must be the same.

noun

informal Back to top  
Something that should not be overlooked or missed: this video is a must for parents
More example sentences
  • The washbag should only contain absolute musts and with the current climate no scissors, razor blades, penknives, etc unless you want them confiscated.
  • They say ‘defense’ and ‘consolidation’ are musts for a global game.
  • When determining which media tools are right for your camp, consider the following list of musts.
Synonyms
not to be missed, very good;
a necessity, essential, a requirement, a requisite

Origin

Old English mōste, past tense of mōt 'may', of Germanic origin; related to Dutch moeten and German müssen.

Phrases

I must say

see say.

must needs do something

see needs.

Definition of must in:

There are 4 main definitions of must in English:

must2

Syllabification: must
Pronunciation: /məst
 
/

noun

Grape juice before or during fermentation.

Origin

Old English, from Latin mustum, neuter (used as a noun) of mustus 'new'.

Definition of must in:

There are 4 main definitions of must in English:

must3

Syllabification: must
Pronunciation: /məst
 
/

noun

Origin

early 17th century: back-formation from musty.

Definition of must in:

There are 4 main definitions of must in English:

must4

Syllabification: must
Pronunciation: /məst
 
/
(also musth)

noun

The frenzied state of certain male animals, especially elephants or camels, that is associated with the rutting season: a big old bull elephant in must
More example sentences
  • Allow only male elephants under the age of fourteen to carry and interact with tourists if the Thai mahouts are unwilling or unable to tell when their male elephants are in musth.
  • Males in musth actively seek mating opportunities and become much more aggressive toward other bulls.
  • During sexually active periods, known as musth, males spend much of their time searching for mates.

adjective

Back to top  
(Of a male elephant or camel) in a frenzied state during rutting season.
More example sentences
  • ‘One musth male expressed his displeasure by musth-rumbling every time a minibus departed from the lodge two kilometers [1.2 miles] away,’ Poole said.

Origin

late 19th century: via Urdu from Persian mast 'intoxicated'.

Definition of must in: