effectual in WordNet English dictionary

1. 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"
   effective  effectual  efficacious 
   
2. having legal efficacy or force
   "a sound title to the property"
   legal  sound  effectual