DictionaryAI

must

MUST/mʌst/

Verbmust, musting, musted

Noun pluralmusts

7 meanings of must

Practice

  1. 1
    have toverbauxiliarymodal
    Used to say that something is necessary or required, because of a rule, a duty or the situation.

    All visitors must sign in at reception.

    Passengers must wear a seat belt or face a fine.

    UsageNo -s and no to: she must go (not incorrect: she must to go). Mustn't forbids; don't have to means not needed.

    Note

    Here a past tense has settled into the present. Old English mōste meant 'had to.' It was the past of mōtan, a verb that covered being allowed as readily as being compelled.

    Checked 2 Nov 2026 · 3 facts

    • Must developed from a past-tense form that acquired present-tense use. en.wikipedia.org
    • Old English mōste meant 'had to' and was the past tense of mōtan. en.wiktionary.org
    • Old English mōtan could express both permission and compulsion. en.wiktionary.org
  2. 2
    surely trueverbauxiliarymodal
    Used to infer that something is very likely or certain to be true.

    You must be tired after such a long drive.

    That must be the new neighbor.

    UsageFor conclusions about the past, use must have + past participle: she must have left. For negative conclusions, can't is common: it can't be him.

    Note

    Necessity is read off a clue here rather than imposed by a rule: the doorbell rings, so it must be Dad. The speaker is not obliged to do anything; they are drawing a conclusion.

  3. 3
    essentialnounauxiliarymodalcountable
    Something mandatory, required or strongly recommended ('a map is a must'); plural 'musts'.

    Booking ahead is a must in August.

    Her list of musts filled a page.

    UsageMostly in X is a must: booking ahead is a must. The plural musts works too.

    Similarnecessity, imperative

    Note

    In I Am a Fugitive from a Chain Gang (1932), a character declares there are 'no musts in my life.' Imperative and necessity are its weightier synonyms, and its opposite is a no-no.

    Checked 2 Nov 2026 · 2 facts

  4. 4
    verb
    Used to urge someone to try or do something, or to invite them warmly, because the speaker thinks it is excellent or well worth it.

    If you're ever in Chicago, you must see the Art Institute; it's wonderful.

    You simply must join us at the lake house this summer.

    UsageOften with simply or really: you simply must come. In an invitation it can sound pressing.

    Note

    Here the obligation is a compliment: nobody is required to see the Art Institute, but the speaker insists because it is so good.

    Checked 3 Nov 2026 · 1 fact

Less common meanings

  1. 5
    grape juicenounauxiliarymodalcountable or uncountable
    Fruit juice, usually from grapes, that will ferment or is fermenting into wine.

    The must is pressed from the grapes within hours of picking.

    Red wine takes its color from skins left in the must.

    Note

    Latin mustum lies behind this word, and it entered English twice, once into Old English and again through Old French. It names juice at the vat stage, before or during fermentation. Longfellow, rendering Ovid, pictures a land where no 'fermenting must' fills and overflows the deep vats. Its shared spelling with the modal is coincidence, because the two words come from entirely separate sources.

    Checked 31 Oct 2026 · 4 facts

    • The wine noun derives from Latin mustum through both Old English and Old French. en.wiktionary.org
    • Longfellow used 'fermenting must' in a translation of Ovid. gutenberg.org
    • The line explicitly denies this: 'No fermenting must fills and o'erflows the deep vats.' gutenberg.org
    • The wine noun and the modal have separate origins. en.wiktionary.org
  2. 6
    damp smellnounauxiliarymodalcountable or uncountable
    Mustiness: the stale, damp, moldy smell or state of something shut away, or a thing gone musty.

    Open the windows and let the must out.

    When we finally opened the attic door, the smell of must and old paper hit us.

    Oppositefreshness

    Note

    The staleness goes with musty, whose origin is uncertain. It may share Latin mustum with the grape-juice sense, perhaps blended with a Latin word for moldy. It has no connection with the modal of obligation, which descends from an Old English verb instead. The noun can be counted or not; counted, it names a musty thing rather than the quality itself.

    Checked 3 Nov 2026 · 5 facts

  3. 7
    verbauxiliaryintransitivemodal
    To become musty and stale with damp, or to make something musty.

    Similarmildew

Practice

Can you tell the meanings of must apart? Answer 3 quick questions from this page, or write your own sentence and AI will check it.

Origins

Meanings 1–4

Must was once a past tense. Old English mōtan meant to be allowed, able or compelled, and its past form mōste ("had to") became Middle English moste ("must", literally "had to"), the past of moten ("to have to"). The Proto-Germanic verb was *mōtaną. Dutch moest, German musste and Swedish måste are related.

Checked 1 Nov 2026 · 8 facts

Meanings 5–7

Both Old English and Old French had the word must (French also had most), and both took it from Latin mustum. The two together produced Middle English must.

Checked 1 Nov 2026 · 3 facts