▪ an action designed to achieve efficiency: "the reforms will lead to efficiencies and savings"
▪ the ratio of the useful work performed by a machine or in a process to the total energy expended or heat taken in:"the boiler has an efficiency of 45 per cent"
Word Originlate 16th century (in the sense ‘the fact of being an efficient cause’): from Latin efficientia, from efficere ‘accomplish’ (see effect).