The Oxford Thesaurus An A-Z Dictionary of Synonyms - effective adj.

1) effectual, efficacious, productive; capable, useful, serviceable, competent, operative, able, functional, efficient: The effective life of the battery is six months. 2) impressive, remarkable, noticeable, conspicuous, outstanding, striking, powerful, compelling, moving, telling, effectual: The stage setting was very effective. 3) operative, operational, in operation, functioning, real, actual, essential, basic, true: The monthly interest may seem low, but the effective annual rate is much higher.