Established by convention
accustomed, prevailing, accepted, customary, regular, standard, orthodox, traditional, habitual, wonted, normal, typical, expected, usual, routine, general, everyday, commonplace, ordinary, plain, current, popular, prevalent, predominant, expected, well-known, stereotyped, in established usage; see also sense 2, accepted, common 1, familiar 1, habitual 1, popular 3, traditional 2.
Antonyms atypical, unusual*, unpopular.
In accordance with convention
established, sanctioned, correct, confirmed, seemly, decorous, proper, decent, fit, fitting, fixed, standard, set, conforming, conformable, fashionable, formal, ritual, ceremonious, right, precise, ceremonial, not taboo, prearranged, undivergent, undeviating, orderly, arranged, stiff, rigid, stylish, modish, comme il faut (French), according to Hoyle*; see also sense 1, fit 1.
Antonyms relaxed, unconventional, spontaneous.
Devoted to or bound by convention
formal, stereotyped, unoriginal, orthodox, narrow, narrow-minded, illiberal, dogmatic, conformist, insular, parochial, strict, rigid, puritanical, inflexible, hidebound, conservative, traditional, doctrinal, conforming, literal, believing, unheterodox, not heretical, canonical, scriptural, literal, bigoted, obstinate, straight-laced, stodgy, stuffy*, straight*, square*, button-down*; see also conservative, polite 1, prejudiced.
Antonyms liberal*, broad-minded, unconventional.
Formalized; said especially of artistic designs
conventionalized, stylized, regularized; see regular 3.