133 entries under adjective topic. ×

23
fundamental(simple, plain, important, straightforward)
22
basic(simple, plain, base, important)
20
essential(simple, plain, important, significant)
15
primary(simple, plain, base, important)
15
elementary(simple, plain, important, significant)
13
elemental(simple, plain, important, significant)
11
cardinal(noun, important, significant, original)
9
radical(base, important, significant, last)
9
rudimentary(simple, plain, important, significant)
9
inherent(essential, basic, absolute, fundamental)
8
basal(simple, plain, base, important)
8
intrinsic(important, significant, original, essential)
8
primitive(simple, plain, important, significant)
7
bottom(noun, important, significant, original)
7
hidden(fundamental, latent)
7
prime(important, significant, original, essential)
7
principal(important, significant, original, essential)
6
crucial(important, significant, original, essential)
6
foundational(simple, plain, base, important)
6
vital(top, important, significant, original)
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APASmart Define. (2015). underlying thesaurus. Retrieved September 22, 2026, from https://smartdefine.org/underlying/thesaurus/synonyms
ChicagoSmart Define. 2015. "underlying thesaurus" https://smartdefine.org/underlying/thesaurus/synonyms (accessed September 22, 2026).
HarvardSmart Define 2015, underlying thesaurus, Smart Define, viewed 22 September, 2026, <https://smartdefine.org/underlying/thesaurus/synonyms>.
MLASmart Define. "underlying thesaurus" 10 April 2015. Web. 22 September 2026. <https://smartdefine.org/underlying/thesaurus/synonyms>