Middle English effectuel, effectual "efficacious, effective, legally binding," borrowed from Anglo-French effectuel, borrowed from Medieval Latin effectuālis, from Latin effectu-, stem of effectus "achievement, result, " + -ālis
adjective
producing or able to produce a desired effect
effectiveeffectualefficientefficacious mean producing or capable of producing a result. effective stresses the actual production of or the power to produce an effect. effectual suggests the accomplishment of a desired result especially as viewed after the fact.