Definition of effective

< effect

effectively >

ef·fec·tive    (-fktv) KEY 

ADJECTIVE:

1. 1. Having an intended or expected effect.
   2. Producing a strong impression or response; striking: gave an effective performance as Othello.
2. Operative; in effect: The law is effective immediately.
3. Existing in fact; actual: a decline in the effective demand.
4. Prepared for use or action, especially in warfare.

NOUN:

A soldier or a piece of military equipment that is ready for combat: "The 'company' was no more than two platoons of effectives" (Tom Clancy).

OTHER FORMS:
ef·fective·ness or effec·tivi·ty(Noun)

SYNONYMS:
effective, effectual, efficacious, efficient

These adjectives mean producing or capable of producing a desired effect: an effective reprimand; an effectual complaint; an efficacious remedy; the efficient cause of the revolution.