Certain and Unsound
Opposite meaning words
Certain
Certain adjective - Known but not named.
Unsound
Unsound adjective - Not using or following good reasoning.
Usage example: it is clearly unsound to argue that just because a scientific explanation for that phenomenon does not currently exist, no such explanation is possible
Cite this Source
Unsound and Certain. (2016). Retrieved 2026, August 15, from https://thesaurus.plus/related/certain/unsound
Certain & Unsound. N.p., 2016. Web. 15 Aug. 2026. <https://thesaurus.plus/related/certain/unsound>.
Unsound or Certain. 2016. Accessed August 15, 2026. https://thesaurus.plus/related/certain/unsound.
Google Ngram Viewer shows how "certain" and "unsound" have occurred on timeline