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ought; should; obliged, bound, required, or compelled to: You must be on time.; a necessity; vital: A warm coat is a must in this weather.
Not to be confused with:
mussed – messy; untidy; tangled: mussed hair
Abused, Confused, & Misused Words by Mary Embree Copyright © 2007, 2013 by Mary Embree

must 1

1. To be obliged or required by morality, law, or custom: Citizens must register in order to vote.
2. To be compelled, as by a physical necessity or requirement: Plants must have oxygen in order to live.
3. Used to express a command or admonition: You must not go there alone. You simply must be careful.
4. To be determined to; have as a fixed resolve: If you must leave, do it quietly.
a. Used to indicate inevitability or certainty: We all must die.
b. Used to indicate logical probability or presumptive certainty: If the lights were on, they must have been at home.
v.intr. Archaic
To be required or obliged to go: "I must from hence" (Shakespeare).
Something that is absolutely required or indispensable: Promptness on the job is a must. Comfortable boots are a must when going on a hike.

[Middle English moste, from Old English mōste, past tense of mōtan, to be allowed; see med- in Indo-European roots.]

must 2

The quality or condition of being stale or musty.

[Probably back-formation from musty.]

must 3

The unfermented or fermenting juice expressed from fruit, especially grapes.

[Middle English, from Old English, from Latin mustum, from neuter of mustus, new, fresh.]

must 4

Variant of musth.

must 5


[Scottish, from Old French, variant of musc; see musk.]
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.


(mʌst; unstressed məst; məs)
1. used as an auxiliary to express obligation or compulsion: you must pay your dues. In this sense, must does not form a negative. If used with a negative infinitive it indicates obligatory prohibition
2. used as an auxiliary to indicate necessity: I must go to the bank tomorrow.
3. used as an auxiliary to indicate the probable correctness of a statement: he must be there by now.
4. used as an auxiliary to indicate inevitability: all good things must come to an end.
5. (used as an auxiliary to express resolution)
a. on the part of the speaker when used with I or we: I must finish this.
b. on the part of another or others as imputed to them by the speaker, when used with you, he, she, they, etc: let him get drunk if he must.
6. (used emphatically) used as an auxiliary to express conviction or certainty on the part of the speaker: he must have reached the town by now, surely; you must be joking.
7. (foll by away) used with an implied verb of motion to express compelling haste: I must away.
an essential or necessary thing: strong shoes are a must for hill walking.
[Old English mōste past tense of mōtan to be allowed, be obliged to; related to Old Saxon mōtan, Old High German muozan, German müssen]


mustiness or mould
[C17: back formation from musty]


(Brewing) the newly pressed juice of grapes or other fruit ready for fermentation
[Old English, from Latin mustum new wine, must, from mustus (adj) newborn]


(Zoology) a variant spelling of musth
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014



auxiliary v.andv., pres. sing.andpl. 1st, 2nd, and3rd pers. must, auxiliary verb.
1. (used to express obligation or imperative requirement): I must keep my promise. We really must go now.
2. (used to express requirement or compulsion by law, social convention, or morality): The rules must be obeyed. I must say, you look wonderful.
3. (used to express advisability or desirability): You really must read this book.
4. (used to express inevitability, necessity, or compulsion by natural laws): All good things must come to an end. One must eat to live.
5. (used to express logical necessity): There must be some mistake.
6. (used to express strong probability or reasonable expectation): You must be joking. He must be at least 70.
7. (used to express intention or determination, often persistence in something unwelcome): if you must know; Must you repeat everything I say?
8. Archaic. (sometimes used with ellipsis of go, get, or some similar verb readily understood from the context): We must away.
9. necessary; vital: A raincoat is must clothing in this area.
10. something necessary, vital, or required: Getting enough sleep is a must.
[before 900; Middle English most(e), Old English mōste, past tense of Middle English mote, Old English mot mote2, 3rd singular of motan, c. Old Frisian mōta, Old Saxon mōtan to have cause to, must, Old High German muozan may; compare empty]



the juice of grapes or other fruit during fermentation.
[before 900; Middle English, Old English < Latin mustum, short for vīnum mustum new wine]



mold; moldiness; mustiness.



Random House Kernerman Webster's College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.


Must is usually used to say that something is necessary. It can also be used to say that you believe that something is true. Must is called a 'modal'.

1. 'must', 'have to', 'have got to', and 'need to'

The expressions have to, have got to, and need to can sometimes be used with the same meaning as must.

The negative form of must is must not or mustn't. The negative forms of have to and have got to are don't have to and haven't got to. The negative form of need to is need not, needn't or don't need to. However, these negative forms do not all have the same meaning. This is explained below under negative necessity.

2. necessity in the present

Must, have to, have got to, and need to are all used to say that it is necessary that something is done.

I must go now.
You have to find a solution.
We've got to get up early tomorrow.
A few things need to be done before we can leave.

After must you use an infinitive without to. Don't use a to-infinitive. Don't say, for example, 'I must to go now.'

If someone is required to do something regularly, for example as a job or duty, say that they have to do it. Don't use 'must'.

She has to do all the cooking and cleaning.
We always have to write to our grandparents to thank them for our birthday gifts.

If someone is required to do something on a particular occasion, say that they have got to do it or, in formal English and American English, that they have to do it.

I've got to go and see the headmaster.
We have to take all these boxes upstairs.

In formal English, must is used to say that someone is required to do something by a rule or law.

You must submit your application by the end of this month.
3. necessity in the past

If you want to say that something was necessary in the past, you use had to. Don't use 'must'.

She couldn't stay because she had to go to work.
We had to sit in silence.
4. necessity in the future

If you want to say that something will be necessary in the future, you use will have to.

He'll have to go to hospital.
We will have to finish this tomorrow.
5. negative necessity

You use must not or mustn't to say that it is important that something is not done.

You must not be late.
We mustn't forget the tickets.

If you want to say that it is not necessary that something is done, you use don't have to, haven't got to, needn't, or don't need to.

You don't have to eat everything on your plate.
I haven't got to work tomorrow, so I can sleep late.
You don't need to explain.

Be Careful!
Don't use 'must not', 'mustn't', or 'have not to' to say that it is not necessary that something is done. Don't say, for example 'You mustn't explain' when you mean that it is not necessary to explain.

To say that it was not necessary for something to be done on a particular occasion in the past, use didn't have to or didn't need to.

Fortunately, she didn't have to choose.
I didn't need to say anything at all.
See need
6. strong belief

You use must to say that you strongly believe that something is true, because of particular facts or circumstances.

There must be some mistake.
Oh, you must be Gloria's husband.

Have to and have got to can also be used in this way, but not when the subject is you.

There has to be way out.
Money has got to be the reason.

You can use must with be and an -ing form to say that you believe something is happening.

He isn't in his office. He must be working at home.
You must be getting tired.

Be Careful!
Don't use must with an infinitive to say that you believe something is happening. Don't say, for example, 'He isn't in his office. He must work at home'.

To say that you believe something is not true, use cannot or can't. Don't use 'must' or 'have to' with not.

The two statements cannot both be correct.
You can't have forgotten me.
Collins COBUILD English Usage © HarperCollins Publishers 1992, 2004, 2011, 2012
ThesaurusAntonymsRelated WordsSynonymsLegend:
Noun1.must - a necessary or essential thingmust - a necessary or essential thing; "seat belts are an absolute must"
essential, necessary, requisite, necessity, requirement - anything indispensable; "food and shelter are necessities of life"; "the essentials of the good life"; "allow farmers to buy their requirements under favorable conditions"; "a place where the requisites of water fuel and fodder can be obtained"
2.must - grape juice before or during fermentation
grape juice - the juice of grapes
3.must - the quality of smelling or tasting old or stale or mouldymust - the quality of smelling or tasting old or stale or mouldy
staleness - having lost purity and freshness as a consequence of aging
Adj.1.must - highly recommended; "a book that is must reading"
essential - basic and fundamental; "the essential feature"
Based on WordNet 3.0, Farlex clipart collection. © 2003-2012 Princeton University, Farlex Inc.


1. necessity, essential, requirement, duty, fundamental, obligation, imperative, requisite, prerequisite, sine qua non (Latin), necessary thing A visit to the motor museum is a must.
1. ought to, have to, should, need to, be required to, have got to, be obliged to, be compelled to, be under an obligation to Mr. Allen must pay your legal costs.


noun mould, rot, decay, mildew, mustiness, fustiness, fetor, mouldiness The air was heady with the smell of must.
Collins Thesaurus of the English Language – Complete and Unabridged 2nd Edition. 2002 © HarperCollins Publishers 1995, 2002


To be required or compelled to do:
Idioms: have got to, have to, must needs.
1. An act or course of action that is demanded of one, as by position, custom, law, or religion:
The American Heritage® Roget's Thesaurus. Copyright © 2013, 2014 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
أكيد أن ، لا بُد أنضَرورَه، شَيء حَيَويعَلَيْكَ أن، يَجِب أن، من الواجِب أنيَجِبيَجِبُ
deberdeber de (probability)haber detener quetener que (obligation)
kellkötelezõ dolog
e-î nauîsynlegthlÿturverîurverîur, má til
...해야 한다
būtinai turėtibūtinybėprivalėtiprivalomas daiktasreikėti
neatliekama vajadzībanepieciešamība


2 [mʌst]
1. (obligation) → deber, tener que
I must do itdebo hacerlo, tengo que hacerlo
the patient must have complete quietel enfermo debe tener or tiene que tener or requiere silencio absoluto
I must buy some presentstengo que comprar unos regalos
you must come again next yeartienes que volver el año que viene
you mustn't forget to send her a cardno te vayas a olvidar de mandarle una tarjeta
you mustn't touch itno debes tocarlo
"must not be switched off"no debe apagarse
I'll do it if I mustsi me obligan, lo haré, lo haré si es necesario
do it if you musthazlo si es necesario
if you must know, I'm Portuguesepara que lo sepa, soy portugués
one must not be too hopefulno hay que ser demasiado optimista
I really must go nowde verdad que me tengo que ir ya
I must say, he's very irritatingtengo que decir que es muy irritante
why must you always be so rude?¿por qué tienes que ser siempre tan maleducado?
2. (probability) → deber de
you must be tireddebes de estar cansado
it must be cold up theredebe de hacer frío allí arriba
he must be there by nowya debe de estar allí
it must be eight o'clock by nowya deben de ser las ocho
but you must have seen her!¡pero debes de haberla visto!
there must be a reasondebe de haber or tiene que haber una razón
B. N this programme is a mustno hay que perderse este programa, este programa hay que verlo
Collins Spanish Dictionary - Complete and Unabridged 8th Edition 2005 © William Collins Sons & Co. Ltd. 1971, 1988 © HarperCollins Publishers 1992, 1993, 1996, 1997, 2000, 2003, 2005


[ˈmʌst](STRONG) [məst]
modal aux vb
I must buy some presents → Il faut que j'achète des cadeaux.
I really must go now → Il faut que j'y aille.
I must do it → il faut que je le fasse, je dois le faire
(urging, inviting)
You mustn't forget to send her a card → N'oublie surtout pas de lui envoyer une carte.
You must come and see us → Venez donc nous voir.
(necessity) if you must ... (= if you have to) → si vous devez absolument ...
If you must smoke → Si vous devez absolument fumer ... (= if you insist) → si tu y tiens absolument
OK, if I must!
BUT d'accord , s'il le faut!.
if you must know → si tu veux tout savoir
must you ...?
Must you be so careless? → Faut-il vraiment que tu sois si négligent?
You must be tired → Tu dois être fatigué.
They must have plenty of money → Ils doivent avoir beaucoup d'argent.
There must be some problem → il doit y avoir un problème.
He must be there by now → Il doit y être maintenant., Il y est probablement maintenant.
I must have made a mistake → J'ai dû me tromper.
(for emphasis) you must be joking! → tu plaisantes!
I must be mad! → je suis fou, ma parole !
to be a must (= necessary) → être indispensable (= not to be missed) → être un must (= something one should try)
The lamb served in a tagine is a must → La tagine d'agneau est à goûter absolument.
Collins English/French Electronic Resource. © HarperCollins Publishers 2005


vb aux present tense only
müssen; you must (go and) see this churchSie müssen sich (dat)diese Kirche unbedingt ansehen; do it if you musttu, was du nicht lassen kannst; if you must knowwenn du es unbedingt wissen willst; must you/I etc? (= really?)ja (wirklich)?; (= do you/I have to?)muss das sein?; we must away (old)wir müssen fort
(in neg sentences) → dürfen; I mustn’t forget thatich darf das nicht vergessen
(= be certain to) he must be there by nower ist wohl inzwischen da; (= is bound to)er ist inzwischen bestimmt da, er muss (wohl) inzwischen da sein; he (surely) must be there by nower MUSS doch inzwischen da sein; I must have lost itich habe es wohl verloren, ich muss es wohl verloren haben; (with stress on must) → ich muss es verloren haben; you must have heard of himSie haben bestimmt schon von ihm gehört; (with stress on must) → Sie müssen doch schon von ihm gehört haben; there must have been five of themes müssen fünf gewesen sein; (about five) → es waren wohl etwa fünf; (at least five) → es waren bestimmt fünf; he must be older than thater muss älter sein; there must be a reason for ites gibt bestimmt eine Erklärung dafür; (with stress on must) → es muss doch eine Erklärung dafür geben; it must be about 3 o’clockes wird wohl (so) etwa 3 Uhr sein, es muss so gegen 3 Uhr sein; I must have been dreamingda habe ich wohl geträumt; I must have been madich muss (wohl) wahnsinnig gewesen sein; you must be crazy!du bist ja or wohl wahnsinnig!
(showing annoyance) → müssen; he must come just nownatürlich muss er gerade jetzt kommen
n (inf)Muss nt; a sense of humour (Brit) or humor (US) /an umbrella is a mustman braucht unbedingt Humor/einen Schirm, Humor/ein Schirm ist unerlässlich; tighter security is a mustbessere Sicherheitskontrollen sind unerlässlich; this novel/film is a must for everyonediesen Roman/diesen Film muss man einfach or unbedingt gelesen/gesehen haben


n (= mustiness)Muffigkeit f


n (Winemaking) → Most m
Collins German Dictionary – Complete and Unabridged 7th Edition 2005. © William Collins Sons & Co. Ltd. 1980 © HarperCollins Publishers 1991, 1997, 1999, 2004, 2005, 2007


1 [mʌst] modal aux vb
a. (obligation) → dovere
I must do it → devo farlo
if you must → se proprio devi
one must not be too hopeful → non bisogna sperare troppo
there must be a reason → ci deve (pur) essere un motivo
I must say → francamente
b. (probability) he must be there by nowdovrebbe essere arrivato ormai
it must be cold up there → dev'essere freddo lassù
I must have made a mistake → devo essermi sbagliato
2. n (fam) this programme/trip is a mustè un programma/viaggio da non perdere


3 [mʌst] n (in wine-making) → mosto
Collins Italian Dictionary 1st Edition © HarperCollins Publishers 1995


(mast) negative short form ˈmustn't (-snt) verb
1. used with another verb to express need. We must go to the shops to get milk.
2. used, usually with another verb, to suggest a probability. They must be finding it very difficult to live in such a small house.
3. used, usually with another verb, to express duty, an order, rule etc. You must come home before midnight; All competitors must be under 15 years of age.
something necessary, essential, or not to be missed. This new tent is a must for the serious camper.
must have
used to state a probability about something in the past. She must have been very young when she got married.
Kernerman English Multilingual Dictionary © 2006-2013 K Dictionaries Ltd.


يَجِبُ muset müssen πρέπει deber täytyä devoir morati dovere ・・・しなければならない ...해야 한다 moeten musieć dever быть обязанным måste ต้อง Zorunda olmak phải 必须
Multilingual Translator © HarperCollins Publishers 2009


v. aux. deber, ser necesario, tener que;
You must take the medicationUsted debe, tú debes tomar la medicina.
English-Spanish Medical Dictionary © Farlex 2012
Collins Multilingual Translator © HarperCollins Publishers 2009
References in periodicals archive ?
Tsai also listed her 'five musts,' uniting the DPP, linking up with social forces to 'make the DPP larger than the DPP,' let the public feel the economic improvements as a result of reforms, protect sovereignty to allow all Taiwanese to choose their own future, and link up with friends overseas who support freedom and human rights in order to turn Taiwan into 'the world's Taiwan.'
MUST is intended to serve as a core municipal bond allocation in investors' portfolios but can also complement traditional core holdings to deliver higher tax-exempt income and risk-adjusted return potential than traditional benchmark products.
In the Urdu category, MUST's Farrukh Awais stood first while second one was also clinched by Mr.
Writers may well be reputed to be an aggregation of distinct and well-defined individuals laboring in compatibility in order to bring forth something on paper exclusively from their cultivatable minds; and Writer Must does give the effect to fit that analogy.
Hand or liquid soaps are definite musts in the bathroom.
Partygoers can also look forward to a range of original hard rock songs from MUST's upcoming album and Black Lime will finish off the event with a selection of well-known rock covers.
The report, "SR1,200 salary set for Indian housemaids," (July 22) has many "musts" for those employers who wish to hire a maid.
The "musts" are: the issue of Syria must be resolved through political means; the future of Syria must be decided by its own people; an inclusive political transition process must be promoted; national reconciliation and Syria's unity must be achieved in Syria.
often ambiguous, conciliatory maybes, no musts, something between the
"High quality rail services and improved connectivity are increasingly important 'musts' for our cities' businesses, especially in terms of access to London and Manchester, and vital for inward investment.
For more tips, read "4 Business Plan Musts" at