A soldier fit for duty
Having the power to produce a required effect or effects.
The pill is an effective method of birth control.
Producing a decided or decisive effect.
The president delivered an effective speech!
Efficient, serviceable, or operative, available for useful work.
How long does it take to make a bunch of civilians an effective military force?
Actually in effect.
The curfew is effective at midnight.
(of a cycle or divisor) Having no negative coefficients.
(for any effective theory) approximate; Not describing the fundamental dynamic changes in some system as they happen.