What is Efficiency?
{{enWiktionary|efficiency}} '''Efficiency''' could mean: * [[Energy efficiency]], useful work per quantity of energy ** [[Energy conversion efficiency]], desired energy output per energy input ** [[Energy conservation]], reducing the use of energy ** [[Electrical efficiency]], useful power output per [[electrical power]] consumed ** [[Fuel efficiency]], converting energy in fuel to kinetic energy or work *** [[Specific impulse]], in propulsion systems, a measure of fuel-efficiency ** [[Volumetric efficiency]], in [[internal combustion engine]] design ** [[Lighting efficiency]], visible light from a light source per unit of power, in lumens per watt ** [[Mechanical efficiency]], the effectiveness of a simple machine, mechanical advantage over ideal mechanical advantage ** [[Thermodynamic efficiency]], useful work per change in heat *** [[Exergy efficiency]], measure of 2nd-law themodynamic loss *** [[Thermal efficiency]], useful work per the higher heating value of the fuel ** [[Radiation efficiency]], ratio of radiated power to power absorbed at the terminals of an antenna * [[Efficiency (aerodynamics)]], for fixed wing aircraft the Lift-to-drag ratio * [[Efficiency (economics)]], a general term, to capture the amount of waste or other undesirable features ** [[Pareto efficiency]], making one individual better off, without making any other individual worse off ** [[Kaldor-Hicks efficiency]], like a less stringent Pareto efficiency ** [[Allocative efficiency]], an optimal distribution of goods ** The optimisation of a [[social welfare function]] ** [[Efficiency wages]], paying workers more than the market rate for increased productivity * [[Efficiency (statistics)]], a measure of desirability of an estimator * [[Efficiency ratio]], expenses as a percentage of revenue, etc. * [[Efficiency Movement]], of the Progressive Era 1890-1932, advocated efficiency in the economy, society and government * [[Material efficiency]], compares material requirements between construction projects or physical processes * [[Textual e