Meanings
adjectiveunefficacious (comparative more unefficacious, superlative most unefficacious)
comparative more unefficacious · superlative most unefficacious
- Not efficacious.
Origin
- Proto-Indo-European*né
- Proto-Indo-European*n̥-
- Proto-Germanic*un-
- Proto-West Germanic*un-
- Old Englishun-
- Middle Englishun-
- Englishun-
- Latinefficāx
- Old Frenchefficacieux
- Englishefficacious
- Englishunefficacious
From un- + efficacious.
Full word history & related roots →Cite this entry
APA
unefficacious. (n.d.). In WatkinsX Dictionary. Retrieved November 3, 2026, from https://dictionary.watkinsx.com/word/unefficacious
MLA
“unefficacious.” WatkinsX Dictionary, https://dictionary.watkinsx.com/word/unefficacious. Accessed November 3, 2026.
Chicago
WatkinsX Dictionary, s.v. “unefficacious,” accessed November 3, 2026, https://dictionary.watkinsx.com/word/unefficacious.
Source: unefficacious on Wiktionary, CC BY-SA 4.0.