Effective and Inefficacious
Opposite meaning words
Effective
Effective adjective - Producing or capable of producing an intended result or having a striking effect.
Usage example: effective steps toward peace
Inefficacious is an antonym for effective.
Inefficacious
Inefficacious adjective - Not producing the desired result.
Usage example: his efforts to restore the neglected houseplant back to health were belated and sadly inefficacious
Effective is an antonym for inefficacious.
Cite this Source
Inefficacious and Effective. (2016). Retrieved 2026, August 16, from https://thesaurus.plus/related/effective/inefficacious
Effective & Inefficacious. N.p., 2016. Web. 16 Aug. 2026. <https://thesaurus.plus/related/effective/inefficacious>.
Inefficacious or Effective. 2016. Accessed August 16, 2026. https://thesaurus.plus/related/effective/inefficacious.
Google Ngram Viewer shows how "effective" and "inefficacious" have occurred on timeline