Effective, a.
Etymology: [L. effectivus: cf. F. effectif.]
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. They are not effective of anything, nor leave no work behind them. Bacon. Whosoever is an effective, real cause of doing his heighbor wrong, is criminal. Jer. Taylor.
Syn. -- Efficient; forcible; active; powerful; energetic; competent. See Effectual.
1 other Webster entry under this spelling
Effective, n.
1. That which produces a given effect; a cause. Jer. Taylor.
2. One who is capable of active service. He assembled his army -- 20,000 effectives -- at Corinth. W. P. Johnston.
3. Etym: [F. effectif real, effective, real amount.] (Com.)
Specie or coin, as distinguished from paper currency; -- a term used in many parts of Europe. Simmonds.
Shades of meaning
Fernald lists effective only as an antonym, under vain.
He lists it without comment; the entries above explain its neighbors.