effective

a.

  1. Having the power to produce an effect or effects; producing a decided or decisive effect; efficient; serviceable; operative; as, an effective force, remedy, speech; the effective men in a regiment.

n.

  1. That which produces a given effect; a cause.
  2. One who is capable of active service.
  3. Specie or coin, as distinguished from paper currency; -- a term used in many parts of Europe.