efficacious

/ɛf.ɪ.ˈkeɪ.ʃəs/adjective

Able to produce the intended result; working well.

Example sentences

“The new treatment proved efficacious in most of the patients tested.”
“Doctors still debate whether vitamin C is efficacious against the common cold.”

Formal and technical; medicine and pharmacology keep it alive. Everyday English says 'effective', and the related noun is 'efficacy'.

Synonyms for efficacious

effective
successful
potent

Antonyms

ineffective
useless

Often confused with efficacious

efficacious vs efficient

Find it in: Advanced English words.

Related words

effervescentLively, cheerful, and overflowing with energy and enthusiasm.effaceTo rub out or wipe away something written or marked, making it impossible to read or see.effusiveExpressing feelings, especially praise or gratitude, in an overflowing and unrestrained way.egregiousStanding out as remarkably bad; shockingly obvious in a negative way.eclecticDrawing on a wide mix of sources, styles, or ideas, choosing whatever seems best from each.ebullientFull of cheerful energy and excitement.