efficacy
Americannoun
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the capacity for producing a desired result or effect.
Short, frequent periods of practice were shown to have greater efficacy than longer and less frequent ones.
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a measure of the success of a vaccine or other pharmaceutical when used in the controlled environment of a clinical trial, as opposed to in the real world.
noun
Other Word Forms
Derived Forms
Etymology
Origin of efficacy
First recorded in 1520–30; from Latin efficācia, from efficāc- (stem of efficāx ) “effective, effectual” + -ia, noun suffix; see efficacious ( def. ), -y 3 ( def. )
Explanation
The degree to which a method or medicine brings about a specific result is its efficacy. You might not like to eat it, but you can't question the efficacy of broccoli as a health benefit. Efficacy is a more formal way to say effectiveness, both of which stem from the Latin verb efficere "to work out, accomplish." The effectiveness, or efficacy, of something is how well it works or brings the results you hoped for. A scientist does research to determine the efficacy of a vaccine or medicine under development. If it is efficacious, it will cure or prevent a disease.
Vocabulary lists containing efficacy
ASVAB Word Knowledge
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Power Suffix: -acy
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This Week in Words: December 30, 2017 - January 5, 2018
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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.
Efficacy measures the maximum response a ligand can elicit, and potency measures the amount of ligand required to elicit half of the maximum response.
From Science Daily • Dec. 21, 2023
Efficacy is one, but other considerations include reusability, keeping the dead animals out of sight, and remote notification that a trap has been activated.
From New York Times • Feb. 27, 2023
The shot did not have a significant impact on infant doctor visits related to respiratory disease: Efficacy was 57.1% at 90 days and 51.3% over 6 months.
From Science Magazine • Nov. 2, 2022
It was an “unholy birth,” writes Mikkael A. Sekeres, an oncologist and a former FDA Oncologic Drugs Advisory Committee chairman, in his new book, “Drugs and the FDA: Safety, Efficacy and the Public’s Trust.”
From Washington Post • Sep. 26, 2022
Besides all this, those Remedies from which the chief Efficacy and Operation against the Disease was expected, still remain’d secret with the Physicians, who thought it no Trouble to prepare them with their own Hands.
From Medicina Flagellata Or, The Doctor Scarify'd by Anonymous
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
