Efficacy and Inefficaciousness

Opposite meaning words

Efficacy noun - Capacity or power to produce a desired effect.

Usage example: concern about the safety and efficacy of the vaccine

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Inefficaciousness is an antonym for efficacy.

Inefficaciousness noun - A lack of efficacy.

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Efficacy is an antonym for inefficaciousness.

Cite this Source

Inefficaciousness and Efficacy. (2016). Retrieved 2026, August 01, from https://thesaurus.plus/related/efficacy/inefficaciousness

Efficacy & Inefficaciousness. N.p., 2016. Web. 01 Aug. 2026. <https://thesaurus.plus/related/efficacy/inefficaciousness>.

Inefficaciousness or Efficacy. 2016. Accessed August 01, 2026. https://thesaurus.plus/related/efficacy/inefficaciousness.

Google Ngram Viewer shows how "efficacy" and "inefficaciousness" have occurred on timeline