47 entries under obligatory topic. ×

10
significant(adjective, big, important, original, substantial)
8
chief(adjective, big, important, significant, substantial)
7
prime(adjective, body, material, important, significant)
7
incumbent
6
de rigueur(expression, adjective, right, essential, required)
6
paramount(adjective, important, significant, original, substantial)
5
conclusive(adjective, demonstration, decisive, required)
5
constraining(adjective, required)
5
elementary(adjective, easy, important, significant, original)
4
called for(verb, expression, phrasal verb, right, essential)
3
bottom-line(adjective, important, significant, original, essential)
3
bounden(required, conclusive)
2
enforced(required, compulsory, mandatory)
2
fixed(expected, predictable, inexorable, required)
2
imperious(required, compulsory, mandatory)
2
incumbent on(expression, adjective, essential, required)
2
prescribed(adjective, expected, predictable, inexorable)
2
suitable(adjective, wanted, needed, compulsory)
1
right(noun, adjective, want, essential, obligation)
1
unalterable(expected, predictable, inexorable, required)
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APASmart Define. (2015). necessary thesaurus. Retrieved September 27, 2026, from https://smartdefine.org/necessary/thesaurus/synonyms
ChicagoSmart Define. 2015. "necessary thesaurus" https://smartdefine.org/necessary/thesaurus/synonyms (accessed September 27, 2026).
HarvardSmart Define 2015, necessary thesaurus, Smart Define, viewed 27 September, 2026, <https://smartdefine.org/necessary/thesaurus/synonyms>.
MLASmart Define. "necessary thesaurus" 2 November 2015. Web. 27 September 2026. <https://smartdefine.org/necessary/thesaurus/synonyms>