Must Definition

mŭst

verb

To be obliged or required by morality, law, or custom.

Citizens must register in order to vote.

American Heritage

To be compelled, as by a physical necessity or requirement.

Plants must have oxygen in order to live.

American Heritage

Used elliptically in the same functions as must.

Shoot if you must.

Webster's New World

To be determined to; have as a fixed resolve.

If you must leave, do it quietly.

American Heritage

Used to indicate inevitability or certainty.

We all must die.

American Heritage

Synonyms:

noun

Something that must be done, had, read, seen, etc.

This book is a must.

Webster's New World

Something that is absolutely required or indispensable.

Promptness on the job is a must. Comfortable boots are a must when going on a hike.

American Heritage

A state of frenzy in animals, esp. in the male elephant, usually associated with sexual heat.

Webster's New World

A musty quality or state; mustiness.

Webster's New World

The juice pressed from grapes or other fruit before it has fermented; new wine.

Webster's New World

Synonyms:

Antonyms:

adjective

That must be done, etc.; necessary; essential.

A book that is must reading.

Webster's New World

In must.

Webster's New World

Other Word Forms of Must

Singular:

must

Plural:

musts

From Middle English moste (“must", literally “had to"), from Old English mōste (“had to"), 1st & 3rd person singular past tense of mōtan (“to be allowed, be able to, have the opportunity to, be compelled to, must, may"). Cognate with Dutch moest (“had to"), German musste (“had to"), Swedish mÃ¥ste (“must, have to, be obliged to"). More at mote.

From Wiktionary
Middle English moste from Old English mōste past tense of mōtan to be allowed med- in Indo-European roots

From American Heritage Dictionary of the English Language, 5th Edition
Middle English from Old English from Latin mustum from neuter of mustus new, fresh

From American Heritage Dictionary of the English Language, 5th Edition
Persian مست (mast, “drunk, inebriated"), from Middle Persian 𐭬𐭮𐭲 (mast).

From Wiktionary
Scottish from Old French variant of musc musk

From American Heritage Dictionary of the English Language, 5th Edition
Old French must, most, from Latin mustum

From Wiktionary
Probably back-formation from musty

From American Heritage Dictionary of the English Language, 5th Edition