Synonyms of efficacious

1 Syllable

going, strong

2 Syllables

big-gun, helpful, big-wheel, hot-dog, valid, puissant, potent, namest, hotdog, namer, virtuous

3 Syllables

active, successful, capable, inerrant, monarchal, sovereigns, efficient, bestselling, influential, clear-sighted, judicious, well-judged, sovereign, powerful, competent, effectual, useful

4 Syllables

predominant, adequate, persuasive, self-governed, exertive, infallible, inerrable, apodictic, convictive, effective, serviceable, providential, energetic, forward-looking

5 Syllables

undeceivable, operative