English▸ adjective required by a legal, moral, or other rule; compulsory:
use of seat belts in cars is now obligatory.
▪ (of a ruling) having binding force:
a sovereign whose laws are obligatory.
▪ often humorous so customary or routine as to be expected of everyone or on every occasion:
after the obligatory preamble on the weather he got down to business.
– ORIGIN late Middle English : from late Latin obligatorius, from Latin obligat- ‘obliged’, from the verb obligare (see oblige).