efficacious

Synonyms

effective, effectual, efficient, fruitful, operative, potent, productive;

Antonyms

fruitless, ineffective, ineffectual, inefficient, inoperative, unfruitful, unproductive, useless;

Near Antonyms

counterproductive;

incapable, incompetent, inexperienced, inexpert, unqualified, unseasoned, unskilled, unskillful;

abortive, bootless, futile, vain;

empty, hollow, idle, pointless, unavailing, unprofitable, unsuccessful;

inoperative, worthless;

Related Words

hyperefficient, ultraefficient;

adequate, capable, competent;

accomplished, adept, consummate, experienced, expert, masterly, practiced (also practised), proficient, skilled, skillful, versed, veteran, virtuoso;

cogent, convincing, killer, sound, striking, telling, valid;

active, dynamic;

useful, working;

applicable, feasible, functional, practicable, practical, realizable, usable (also useable), workable;