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 trials that randomize participants to receive a treatment or a placebo need to change as well, because now that PrEP exists, clinical trial ethics mandate it be offered to everyone.
From Science Magazine • Mar. 7, 2024
"Efficacy and potency have been measured for numerous ligand-receptor signaling systems for several decades. Now we can understand how specific amino acids in a protein's sequence can influence these pharmacological properties," Babu explained.
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
Efficacy data in humans, however, are much more limited, making some researchers and regulatory agencies hesitant about authorizing tecovirimat’s widespread use.
From Scientific American • Aug. 26, 2022
A Spoonful of this Mixture, whose remarkable Efficacy I have been a Witness of, is to be given every half Hour.
From Advice to the people in general, with regard to their health by Tissot, S. A. D. (Samuel Auguste David)
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.
