Etymology: Middle English moste, from Old English mōste, past indicative & subjunctive of mōtan to be allowed to, have to; akin to Old High German muozan to be allowed to, have to
Date: before 12th century
verbal auxiliary1 a: be commanded or requested to <you must stop>b: be urged to : ought by all means to <you must read that book> 2: be compelled by physical necessity to <one must eat to live>: be required by immediate or future need or purpose to <we must hurry to catch the bus> 3 a: be obliged to : be compelled by social considerations to <I must say you're looking well>b: be required by law, custom, or moral conscience to <we must obey the rules>c: be determined to <if you must go at least wait for me>d: be unreasonably or perversely compelled to <why must you argue> 4: be logically inferred or supposed to <it must be time> 5: be compelled by fate or by natural law to <what must be will be> 6: was or were presumably certain to : was or were bound to <if he did it she must have known> 7dialect:may, shall —used chiefly in questionsintransitive verbarchaic: to be obliged to go <I must to Coventry — Shakespeare>