effective

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?
• My effective income after taxes and child support is $500 a month.

Actually in effect.

• effective immediately
• The curfew is effective at midnight.

Having no negative coefficients.

Such that no group element acts trivially.

approximate; Not describing the fundamental dynamic changes in some system as they happen.

a soldier fit for duty

• The Army of the West reached Corinth sometime after the battle of Shiloh. We were 15,000 effectives, and brought Beauregard's effective force up to 45,000 men.