Synonyms of obligatory in English:

obligatory


See definition of obligatory

adjective

1‘use of seat belts in cars is now obligatory’

SYNONYMS
compulsory, mandatory, prescribed, required, demanded, statutory, enforced, binding, incumbent
requisite, necessary, imperative, unavoidable, inescapable, essential
ANTONYMS

voluntary, optional

2‘after the obligatory preamble on the weather he got down to business’

SYNONYMS
customary, traditional, usual, accustomed, routine, familiar, regular, habitual
de rigueur
literary wonted