efficacy

UK: ˈef.ɪ.kə.si | US: ˈef.ɪ.kə.si

Definition

  1. n. the ability to produce a desired or intended result; effectiveness.

Structure
ef <out, from Latin "ex">fic <do/make, from Latin "facere">acy <noun suffix, from Latin "-acia">
Etymology

The word "efficacy" traces back to Latin efficacia, derived from efficax (effective), which combines ex- (out) and facere (to do/make). The core idea is "the power to bring about results." Over time, it entered Middle English via Old French efficacité, retaining its focus on measurable effectiveness. The morpheme -acy (a noun-forming suffix) solidifies its abstract meaning.

Examples

  1. The efficacy of the new vaccine was confirmed in clinical trials.

  2. Critics questioned the efficacy of the government’s economic policies.

  3. Studies measure the efficacy of different teaching methods.

  4. The drug’s efficacy declines if not stored properly.

  5. She praised the efficacy of the team’s problem-solving approach.