efficiency

noun5

1. •
   The extent to which a resource is used for the intended purpose.
2. •
   The ratio of useful work to energy expended. Often given the symbol η.

   • The efficiency of this loudspeaker is 40%.
3. •
   The extent to which time is well used for the intended task.

   • The efficiency of the planning department is deplorable.
4. •
   (US) A one-room apartment.

   • I have an efficiency available June through July.
5. •
   (old-fashioned) The quality of producing an effect or effects.

   • The manner of this divine efficiency being far above us. — 1594