efficacious

Reading level: hard

Estimated CEFR level: C2 — Proficiency

Estimated from word frequency; not an official CEFR classification.

Definition

adjective marked by qualities giving the power to produce an intended effect; -Aldous Huxley
adjective producing or capable of producing an intended result or having a striking effect; -LewisMumford

From Old French efficacieux, from Latin efficāx (“efficacious”) + -ous, from efficere (“to effect, to accomplish”); see effect.

Especially efficacious in heart disease and tic-douloureux. — The Confidence-Man: His Masquerade, Herman Melville
That was sure, efficacious, and free from danger. — Les Misérables, Victor Hugo
A frog similarly applied is supposed to be equally efficacious." — The Prairie Traveler: A Hand-book for Overland Expeditions, Randolph B. (Randolph Barnes) Marcy

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