13
good(sound, right, reasonable, rational, genuine)
12
sound(adjective, calm, good, strong, secure)
11
just(adjective, good, sound, right, reasonable)
11
solid(adjective, calm, good, strong, sound)
10
valid(adjective, good, sound, right, reasonable)
10
well-grounded(adjective, good, reason, proper, logical)
9
cogent(adjective, good, sound, correct, reasonable)
9
plausible(adjective, true, probable)
7
justified(good, correct, reasonable, proper, moral)
7
rational(adjective, sound, reasonable, reason, logical)
7
reasonable(adjective, sound, correct, reason, sensible)
7
reliable(adjective, calm, good, strong, secure)
7
strong(adjective, calm, good, sound, right)
6
firm(adjective, calm, strong, sound, heavy)
6
legitimate(adjective, good, sound, right, reasonable)
6
likely(adjective, true, probable)
6
secure(adjective, calm, good, strong, sound)
6
sensible(adjective, reasonable, reason, natural, valid)
6
stable(adjective, strong, sound, secure, tough)
6
substantial(adjective, calm, good, strong, sound)
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APASmart Define. (2016). well-founded thesaurus. Retrieved September 21, 2026, from https://smartdefine.org/well-founded/thesaurus/synonyms
ChicagoSmart Define. 2016. "well-founded thesaurus" https://smartdefine.org/well-founded/thesaurus/synonyms (accessed September 21, 2026).
HarvardSmart Define 2016, well-founded thesaurus, Smart Define, viewed 21 September, 2026, <https://smartdefine.org/well-founded/thesaurus/synonyms>.
MLASmart Define. "well-founded thesaurus" 29 March 2016. Web. 21 September 2026. <https://smartdefine.org/well-founded/thesaurus/synonyms>