efficacious
adjective
Did you know?
If you guesstimate that efficacious is the effect of combining effective with the suffix -ious, you’re on the right track. Efficacious came to English from the Middle French word efficace (or that word’s Latin source, efficāc- or efficāx), meaning “effective.” (These words ultimately trace back to the Latin verb efficere, “to make, bring about, produce, carry out.”) English speakers added -ious to effectively create the word we know today. Efficacious is one of many, er, eff words that mean “producing or capable of producing a result.” Among its synonyms are the familiar adjectives effective and efficient. Efficacious is more formal than either of these; it’s often encountered in medical writing where it describes treatments, therapies, and drugs that produce their desired and intended effects in patients.
Synonyms
Examples of efficacious in a Sentence
Alison Habens, JSTOR Daily, 31 Oct. 2024
Truth be told, Hinds was skeptical that an efficacious facial could be done in a half-hour.
—Jennifer Weil, WWD, 18 Oct. 2024
Other efforts were less efficacious, but these books and broadcasts worked.
—Andrei Soldatov, Foreign Affairs, 13 May 2022
The likelihood that efficacious treatments will be developed to help patients with unmet needs, such as people living with Alzheimer’s or muscular dystrophy, is severely compromised as a result.
—Wayne Winegarden, Forbes, 9 Sep. 2024
See all Example Sentences for efficacious 
Cite this Entry
“Efficacious.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/efficacious. Accessed 30 Nov. 2024.
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efficacious
adjective
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