effective /ɪˈfɛktɪv/adjective 7noun 1forms 3 adjective7 •working well and bringing about the result someone needsThe pill is an effective method of birth control. •Producing a decided or decisive effect.The president delivered an effective speech! •Actually in effect.The curfew is effective at midnight. •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. •approximate; Not describing the fundamental dynamic changes in some system as they happen. •Having no negative coefficients. •Such that no group element acts trivially. noun1 •a soldier fit for dutyThe 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. — 1876 formseffectives · more effective · most effective