Adjective
1. sufficient to produce a result;
"a man to whom painting was but another and less effectual way of writing dramas or novels or history"2. 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"3. exerting or capable of exerting strong physiological or chemical effects;
"an effectual vaccine"