In an ion-exchange system, a measurement of the effectiveness of a system expressed as the amount of regenerant required to remove a given unit of adsorbed material.

1. Measure of the degree of heat output per unit of fuel when all available oxidizable materials in the fuel have been burned.

2. Ratio of useful energy provided by a dynamic system to the energy supplied to it during a specific period of operation.

The probability that a count will be produced in a counter tube by a specified particle or quantum incident.

The ratio, usually expressed as a percentage, of the useful power output to the power input of a device.

1. An estimator is more efficient than another if it has a smaller variance.

2. An experimental design is more efficient than another if the same level of precision can be obtained in less time or with less cost.

The ratio of the work done by a heat engine to the heat energy absorbed by it. Also known as thermal efficiency.