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Definitions

efficacious

[ef-i-key-shuhs] / ˌɛf ɪˈkeɪ ʃəs /


Usage

What are other ways to say efficacious? The adjective efficacious suggests the capability of achieving a certain end: an efficacious plan, medicine. Effectual is used especially of that which produces the effect desired or intended, or a decisive result: An effectual bombardment silenced the enemy. Effective is applied to a person or a thing that has the power to, or which actually does, produce an effect: an effective boss, remedy, speech. Efficient (applied also to persons) implies the skillful use of energy or industry to accomplish desired results with little waste of effort: efficient methods; an efficient manager. 

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

She starts by noting that the Voting Rights Act is, or was. one of the most consequential, efficacious, amply justified exercises of federal legislative power in the nation’s history.

From Slate • Apr. 30, 2026

Lilly is also developing a highly efficacious injection called retatrutide that targets GIP and GLP-1 — both of which are activated by tirzepatide — in addition to glucagon.

From MarketWatch • Apr. 1, 2026

Instead of manipulating government for their own narrow interests, the rich can add a distinctively independent-minded, public-spirited and efficacious set of voices to the national debate.

From The Wall Street Journal • Feb. 17, 2026

“If something was to be made available and shown to be efficacious and safe, I think there would be wide use of it,” Jonker says.

From Science Magazine • May 20, 2024

“I do thank you for taking the time, Pomona,” Slughorn was saying courteously, “most authorities agree that they are at their most efficacious if picked at twilight.”

From "Harry Potter and the Half-Blood Prince" by J.K. Rowling




Vocabulary lists containing efficacious