54 entries under fundamental topic. ×

5
original(adjective, simple, plain, important, significant)
4
central(adjective, top, important, significant, original)
4
constitutional(adjective, important, significant, original, essential)
4
indispensable(adjective, important, significant, original, essential)
4
key(adjective, important, significant, original, essential)
4
main(adjective, top, original, essential, basic)
4
necessary(adjective, important, significant, original, essential)
3
capital(adjective, essential, key, main)
3
concealed(adjective, latent)
2
chief(adjective, top, essential, prime, vital)
2
congenital(adjective, essential, basic, absolute)
2
inborn(adjective, essential, basic, absolute)
2
innate(adjective, essential, basic, absolute)
2
lurking(adjective, latent)
2
material(adjective, essential, basic, absolute)
2
needful(adjective, latent)
2
root(adjective, latent)
2
substratal(adjective, simple, plain, important, significant)
2
veiled(adjective, latent)
1
bottom-line(adjective, important, original, basic, vital)
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APASmart Define. (2015). underlying thesaurus. Retrieved September 24, 2026, from https://smartdefine.org/underlying/thesaurus/synonyms
ChicagoSmart Define. 2015. "underlying thesaurus" https://smartdefine.org/underlying/thesaurus/synonyms (accessed September 24, 2026).
HarvardSmart Define 2015, underlying thesaurus, Smart Define, viewed 24 September, 2026, <https://smartdefine.org/underlying/thesaurus/synonyms>.
MLASmart Define. "underlying thesaurus" 10 April 2015. Web. 24 September 2026. <https://smartdefine.org/underlying/thesaurus/synonyms>