119 entries under noun topic. ×

17
reason(information, cause, start, reason)
13
enigma(trouble, informal, challenge, question)
10
ground(cause, start, reason, idea)
9
mystery(trouble, difficulty, reason, informal)
8
wherefore(adverb, information, cause, start)
8
riddle(trouble, challenge, question, secret)
6
mystification(trouble, challenge, question, secret)
6
problem(trouble, challenge, question, secret)
6
proof(cause, reason, informal, idea)
6
puzzlement(trouble, challenge, question, secret)
5
poser(trouble, difficulty, challenge, question)
4
argument(information, cause, reason, idea)
4
cause(start, reason, base, call)
4
closed book(expression, trouble, challenge, question)
4
explanation(cause, basis, justification, grounds)
4
how(adverb, reason)
4
rationale(cause, reason, idea, case)
3
purpose(cause, consideration, purpose, basis)
3
brain-teaser(trouble, challenge, puzzle)
3
intention(cause, purpose, basis, planned)
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APASmart Define. (2016). why thesaurus. Retrieved September 25, 2026, from https://smartdefine.org/why/thesaurus/synonyms
ChicagoSmart Define. 2016. "why thesaurus" https://smartdefine.org/why/thesaurus/synonyms (accessed September 25, 2026).
HarvardSmart Define 2016, why thesaurus, Smart Define, viewed 25 September, 2026, <https://smartdefine.org/why/thesaurus/synonyms>.
MLASmart Define. "why thesaurus" 2 February 2016. Web. 25 September 2026. <https://smartdefine.org/why/thesaurus/synonyms>