The property of being effective, of achieving results. / The capacity or potential for achieving results. / The degree to which something achieves results.

plural of effectiveness

(dated, 1600s) Capable of being done or achieved.

(dated, 1600s) Capability of being done or achieved.

plural of effective

Alternative form of effector

plural of effectivity

Operating or functioning; in force; in play.

For all practical purposes; in practice; actually; essentially; basically.

Having the power to produce a required effect or effects. / Producing a decided or decisive effect. / Efficient, serviceable, or operative, available for useful work. / Actually in effect.