"efficacious" in the adjective sense
1. efficacious
marked by qualities giving the power to produce an intended effect
"written propaganda is less efficacious than the habits and prejudices...of the readers"-Aldous Huxley
"the medicine is efficacious in stopping a cough"
2. 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"
Source: WordNet® (An amazing lexical database of English)
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