An Etymological Dictionary of Astronomy and Astrophysics

1. The state or quality of being efficient; competence. Compare → effectiveness.
   

Of a machine, engine, or device, the ratio of the physical quantity which may be stored, transferred, or transformed to the total input quantity.

Etymology (EN): L efficientia, from efficient-, → effect,

• -ia “-y,” an E. suffix of adjectives.

Etymology (PE): Kârâyi, from kârâ “efficient,” from kâr, → work + â present stem of âmadan “to come,” from Av. ay- “to go, to come,” aēiti “goes,” O.Pers. aitiy “goes,” Skt. e- “to come near,” eti “arrival,” Gk. eimi “I go,” L. eo “I go,” Tokharian AB i-; PIE *ei- “to go, to walk.”