Having an intended or expected effect. Producing a strong impression or response; striking: gave an effective performance as Othello. Operative; in effect: The law is effective immediately. Existing in fact; actual: a decline in the effective demand. Prepared for use or action, especially in warfare. A soldier or a piece of military equipment that is ready for combat: "The 'company' was no more than two platoons of effectives\u201d ( Tom Clancy).