obligatory

Definitions

Required by a legal, moral, or other rule; compulsory.

So customary or routine that it is expected or required by social convention.

Examples

It is obligatory for all employees to attend the safety training session.

The final chapter provides an obligatory summary of the main arguments presented in the book.

Synonyms

mandatory compulsory required binding necessary essential imperative

Antonyms

optional voluntary discretionary elective noncompulsory unnecessary dispensable