efficacy
UK[ˈef.ɪ.kə.si]US[ˈef.ɪ.kə.si]
n
The ability, especially of a medicine or a method, to produce the desired result or effect.
Morpheme Breakdown
effic
acy
effic
work, accomplish
acy
state or quality
Etymology
The word "efficacy" traces its lineage directly to the Latin verb efficere, meaning "to accomplish, work out, or bring about." This verb itself is a compound of ex- (out) and facere (to do or make), a fundamental verb from the Proto-Indo-European root dʰeh₁- (to put, place, set). The suffix -acy was adopted into English via Old French from Latin noun-forming endings denoting a state or quality. Thus, the literal construction "the state of accomplishing (work) out" evolved logically into the modern abstract sense denoting the capacity or power to produce a desired effect, a concept central to fields like medicine, policy, and technology.
Analysis
Structure: effic (work, accomplish) + acy (state or quality)
- effic: From Latin efficere (to accomplish, bring about), combining ex- (out) + facere (to do, make). In this word, it functions as the core root meaning "to produce an effect."
- acy: A noun-forming suffix of Latin origin (-atia, -acia), indicating a state, quality, or condition.
Examples
The efficacy of the new vaccine was confirmed through extensive clinical trials.
Many people question the efficacy of those administrative reforms.
The study measured the efficacy of different teaching methods.