Adjective

Middle English best, beste, going back to Old English betst, best, (as weak adjective) betsta, betesta, going back to Germanic *batista-, superlative degree of the adjective seen in the comparative *batizōn better entry 1, whence also Old Frisian best, bēst "best," Old Saxon betst, best, Old High German bezzisto, Old Icelandic beztr, baztr, Gothic batista

Adverb

Middle English, going back to Old English betst, betest, derivative of betst, best best entry 1

Noun

Middle English, going back to Old English betste, derivative of betst, best best entry 1

Verb

derivative of best entry 1, after better entry 2

Auxiliary verb

by ellipsis from had best

Adjective

before the 12th century, in the meaning defined at sense 1

Adverb

before the 12th century, in the meaning defined at sense 1

Noun

before the 12th century, in the meaning defined at sense 2

Verb

1863, in the meaning defined above

Auxiliary Verb

1897, in the meaning defined above