Definition of efficacy
: the power to produce an effect
Examples of efficacy in a Sentence
In the planner's view, Rumsfeld had two goals: to demonstrate the efficacy of precision bombing and to “do the war on the cheap.” —Seymour M. Hersh, New Yorker, 7 Apr. 2003
Vaccines exist, but their efficacy against aerosolized plague is unknown. —Sharon Begley et al., Newsweek, 8 Oct. 2001
… efficacy does not have to be demonstrated before homeopathic products are marketed. —Alison Abbott et al., Nature, 26 Sept. 1996
questioned the efficacy of the alarms in actually preventing auto theft
Recent Examples of efficacy from the Web
The curriculum is specifically designed toward fostering character development and responsibility geared to elevating individual empowerment, efficacy and self-esteem.
Additionally, rarely in use of force situations is there agreement from all the parties involved as to the appropriateness, efficacy, or necessity of its use.
The comment and the talking points were meant to undercut the efficacy of the Paris agreement, a claim that Reilly says is wrong.
In addition, sunscreen efficacy decreases in the water or with sweating.
And despite their diminishing efficacy, over-the-counter lice shampoos remain the first response recommended by most doctors, health plans and even the American Academy of Pediatrics.
Still, Lewin is skeptical of its efficacy, in part because the herbal proportions aren’t labeled.
As much as his efficacy in front of the goal, and the characteristic imagination in his play, his undimmed appetite for the battle has impressed.
Data such as this supports the belief in and bolsters the efficacy of familial searching to produce valuable leads.
These example sentences are selected automatically from various online news sources to reflect current usage of the word 'efficacy'. Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.
Origin and Etymology of efficacy
First Known Use: 13th century
EFFICACY Defined for English Language Learners
Definition of efficacy for English Language Learners
: the power to produce a desired result or effect
Seen and Heard
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