- effectual - sufficient to produce a result; "a man to whom painting was but another and less effectual way of writing dramas or novels or history"
Antonym: ineffectual
- effective, effectual, efficacious - producing or capable of producing an intended result or having a striking effect; "an air-cooled motor was more effective than a witch's broomstick for rapid long-distance transportation"-LewisMumford; "effective teaching methods"; "effective steps toward peace"; "made an effective entrance"; "his complaint proved to be effectual in bringing action"; "an efficacious law"
- effectual - exerting or capable of exerting strong physiological or chemical effects; "an effectual vaccine"
Antonym: impotent (indirect, via potent)