efficiency

In the plural it becomes the language of budgets and reorganizations, where efficiencies are particular savings to be found. DeJoy, head of the Postal Service, wrote to Congress in 2025 of "identifying and achieving further efficiencies." In the uncountable singular it names the general quality. The word comes from Latin efficientia. Its opposites are the neutral inefficiency and the blunter wastefulness.

Applied to people and organizations, it describes brisk, orderly work rather than thrift. H. A. Vallance, crossing Denmark in the Railway Magazine of 1951, found a station hall giving an impression "of efficiency, neatness and cleanliness." The phrase with efficiency works like an adverb: Phil McNulty's BBC Sport report has England completing "the job with efficiency." The word also draws harsh verdicts, as in a department whose efficiency is deplorable.

An engineer's number rather than a judgment: useful output divided by input, written η and quoted as a fraction or a percentage, as in a loudspeaker rated at 40%. Some energy is always lost, typically as heat, so no real machine reaches 1, or 100%. Unlike the everyday sense, this one is measured rather than praised: you calculate a motor's efficiency.

A US rental word, short for efficiency apartment and counted like any other unit, as in "fully-furnished efficiencies." Studio apartment is the broader synonym. In the UK and Ireland the nearest equivalent is bedsit. Because this sense is a countable noun for a place, it takes an article and a plural freely, unlike the abstract senses of the word.