Synonyms|312Antonyms|117|Broader|4Narrower|13Related|364

5 entries under optional topic. ×

7
voluntary(adjective, willing, involuntary)
3
unnecessary
2
nonessential
1
unrequired
0
free
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APASmart Define. (2015). obligatory thesaurus. Retrieved September 24, 2026, from https://smartdefine.org/obligatory/thesaurus/antonyms
ChicagoSmart Define. 2015. "obligatory thesaurus" https://smartdefine.org/obligatory/thesaurus/antonyms (accessed September 24, 2026).
HarvardSmart Define 2015, obligatory thesaurus, Smart Define, viewed 24 September, 2026, <https://smartdefine.org/obligatory/thesaurus/antonyms>.
MLASmart Define. "obligatory thesaurus" 14 April 2015. Web. 24 September 2026. <https://smartdefine.org/obligatory/thesaurus/antonyms>