The story
- Proto-Indo-European*h₁éǵʰ
- Proto-Indo-European*h₁éǵʰs
- Proto-Italic*eks
- Latinex
- Latinex-
- Proto-Indo-European*dʰeh₁-
- Proto-Indo-European*dʰeh₁k-
- Proto-Indo-European*dʰh₁kyéti
- Proto-Italic*θakjō
- Proto-Italic*fakjō
- Latinfaciō
- Latinefficiō
- Latineffectīvu
- Frencheffectif
- English todayeffective
From French effectif, from Latin effectīvus (“productive; effective”), from efficiō (“to make; to bring about”), equivalent to effect + -ive.
Etymology from Wiktionary, CC BY-SA 4.0.