efficacious

[ ef-i-key-shuhs ]

See synonyms for: efficacious efficaciously efficaciousness on Thesaurus.com

adjective

capable of having the desired result or effect; effective as a means, measure, remedy, etc.: The medicine is efficacious in stopping a cough.

Origin of efficacious

First recorded in 1520–30; from Latin efficāci- (stem of efficax ) “effectual.” See efficient, -acious

Other words from efficacious

ef·fi·ca·cious·ly, adverb
ef·fi·ca·cious·ness, noun
non·ef·fi·ca·cious, adjective
non·ef·fi·ca·cious·ly, adverb
un·ef·fi·ca·cious, adjective
un·ef·fi·ca·cious·ly, adverb

Words Nearby efficacious

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use efficacious in a sentence

It’s a huge ask of a drug that it be so safe and so efficacious that you can give it to everybody.
Why it’s still so hard to find treatments for early COVID-19 | Tina Hesman Saey | July 27, 2021 | Science News
By early 2020, we had a tremendous amount of data showing that in the mouse model that we had developed, these mRNA spike vaccines were really efficacious in protecting against lethal MERS-CoV infection.
“We never created a supervirus.” Ralph Baric explains gain-of-function research. | Rowan Jacobsen | July 26, 2021 | MIT Technology Review
In a release on May 25, Moderna says its vaccine is safe and efficacious among 12- to 18-year olds.
Moderna Says Its COVID-19 Vaccine Is Safe and Works For Teens | Alice Park | May 25, 2021 | Time
If the studies show the new vaccine could be stable and efficacious at refrigerated temperatures, that could increase the number of places that could vaccinate with Moderna’s shot.
Moderna Is Testing a New Version of Its COVID-19 Vaccine That Wouldn’t Require Ultra-Cold Storage | Alice Park | April 29, 2021 | Time
Several days later, however, the company issued another press release including additional data that showed the vaccine is 76% efficacious in protecting people from disease.
Vaccine Safety Board Chides AstraZeneca for Using 'Outdated' Data in Press Release About its COVID-19 Shot | Alice Park | March 23, 2021 | Time

But Michele Bachmann, who has been a wallflower of late, may point the way to a more efficacious line of attack: crony capitalism.
2 Candidates—2 Republican Parties | Paul Begala | September 13, 2011 | THE DAILY BEAST
I asked him if he thought cattle cars would be an efficacious means of transporting the Palestinians to their new homes.
The Wildest Moments From CPAC | Max Blumenthal | March 2, 2009 | THE DAILY BEAST
He inclines to the use of the tepid bath, as likely to be the most generally efficacious.
The Ladies' Book of Etiquette, and Manual of Politeness | Florence Hartley
I know not how to offer advice, and I am incapable of giving any efficacious help.
Private Letters of Edward Gibbon (1753-1794) Volume 1 (of 2) | Edward Gibbon
I can say from experience, that it is a powerful sudorific, and very efficacious in a cold.
Travels through the South of France and the Interior of Provinces of Provence and Languedoc in the Years 1807 and 1808 | Lt-Col. Pinkney
However much the theologian may believe in prayer, he cannot deny that it is less efficacious than action.
Ancient Faiths And Modern | Thomas Inman
The commissioners regarded the land purchase act as embodying the most simple and efficacious remedy for existing evils.
History of Prince Edward Island | Duncan Campbell

British Dictionary definitions for efficacious

efficacious

/ (ˌɛfɪˈkeɪʃəs) /

adjective

capable of or successful in producing an intended result; effective as a means, remedy, etc

Origin of efficacious

C16: from Latin efficāx powerful, efficient, from efficere to achieve; see effect

Derived forms of efficacious

efficaciously, adverb
efficaciousness, noun

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

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