Meaning of MUST in English

I. verb (present & past all persons ~) 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 auxiliary 1. be commanded or requested to , be urged to ; ought by all means to , be compelled by physical necessity to , 3. be obliged to ; be compelled by social considerations to , be required by law, custom, or moral conscience to , be determined to , be unreasonably or perversely compelled to , be logically inferred or supposed to , be compelled by fate or by natural law to , was or were presumably certain to ; was or were bound to , may , shall , intransitive verb to be obliged to go , II. noun Date: 1616 an imperative need or duty ; requirement , an indispensable item ; essential , III. noun Etymology: Middle English, from Old English, from Latin ~um Date: before 12th century the expressed juice of fruit and especially grapes before and during fermentation, IV. noun Etymology: Middle English (Scots) moist, from Middle French ~, alteration of musc musk Date: 15th century musk , mold , ~iness

Merriam Webster. Explanatory English dictionary Merriam Webster.      Толковый словарь английского языка Мерриам-Уэбстер.