Invalid and Well-founded

Opposite meaning words

Invalid adjective - Not using or following good reasoning.

Usage example: an argument which has one untrue premise is invalid

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Well-founded is an antonym for invalid.

Well-founded adjective - According to the rules of logic.

Usage example: even a well-founded argument can lead to an erroneous conclusion if one of the premises is incorrect

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Invalid is an antonym for well-founded.

Cite this Source

Well-founded and Invalid. (2016). Retrieved 2026, August 13, from https://thesaurus.plus/related/invalid/well-founded

Invalid & Well-founded. N.p., 2016. Web. 13 Aug. 2026. <https://thesaurus.plus/related/invalid/well-founded>.

Well-founded or Invalid. 2016. Accessed August 13, 2026. https://thesaurus.plus/related/invalid/well-founded.