COMPULSORY
compulsory, mandatory, required
(adjective) required by rule; “in most schools physical education is compulsory”; “attendance is mandatory”; “required reading”
Source: WordNet® 3.1
Etymology
Adjective
compulsory (comparative more compulsory, superlative most compulsory)
Required; obligatory; mandatory.
Having the power of compulsion; constraining.
Synonyms
• mandatory
Antonyms
• (required): optional
Noun
compulsory (plural compulsories)
Something that is compulsory or required.
Source: Wiktionary
Com*pul"so*ry, a. Etym: [LL. compulsorius.]
1. Having the power of compulsion; constraining.
2. Obligatory; enjoined by authority; necessary; due to complusion.
This contribution therestening fall infinitely short of their hopes,
they soon made it compulsory. Burke.
Source: Webster’s Unabridged Dictionary 1913 Edition