Sunday Word: Efficacious
May. 17th, 2026 11:14 amefficacious [ef-i-key-shuhs]
adjective:
capable of having the desired result or effect; effective as a means, measure, remedy, etc
Examples:
And on a less efficacious, more aesthetic note, many of these natural exfoliating formulas often deliver the same sleek aesthetics in their packaging and experience as prestige skin-care products. (Conçetta Ciarlo, Why I'm Opting for Exfoliating Deodorants This Spring, Vogue, March 2026)
At the end of the day, to suggest that plant medicine is not efficacious feels pretty silly to me. (Rachel King, The founder of wellness startup Mab & Stoke on the growth of 'pay what you can' options during the pandemic, Fortune, September 2020)
The muses may hold a pen in one hand and a smoke, or steaming mug, in the other - herbal remedies continue to be efficacious for writer’s block. (Alison Habens, A Brief History of the Muses, JSTOR Daily, October 2024)
Certainly the myth of the cowboy is an efficacious myth, one based first of all upon a deep response to nature. (Larry McMurtry, American Cowboys, Harper's Magazine, September 1968)
One of the best and most efficacious remedies would be for the person who has taken possession of them to go there to live. (Niccolò Machiavelli, The Prince)
Origin:
'sure to have the desired effect' (often of medicines), 1520s, from Latin efficaci-, stem of efficax 'powerful, effectual, efficient,' from stem of efficere 'work out, accomplish' + -ous. (Online Etymology Dictionary)
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. (Merriam-Webster)

