capable of having the desired result or effect; effective as a means, measure, remedy, etc.: The medicine is efficacious in stopping a cough.
- 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
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the vaccine is 76% efficacious in protecting people from disease.Vaccine Safety Board Chides AstraZeneca for Using 'Outdated' Data in Press Release About its COVID-19 Shot | Alice Park | March 23, 2021 | Time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.
I asked him if he thought cattle cars would be an efficacious means of transporting the Palestinians to their new homes.
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.
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
capable of or successful in producing an intended result; effective as a means, remedy, etc
- 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