efficacious

[ ef-i-key-shuhs ]

/ ˌɛf ɪˈkeɪ ʃəs /

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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.

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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, adverbef·fi·ca·cious·ness, nounnon·ef·fi·ca·cious, adjectivenon·ef·fi·ca·cious·ly, adverb

un·ef·fi·ca·cious, adjectiveun·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

A vaccine that is highly efficacious, if taken by a very, very high percentage of people, could potentially crush this outbreak — similar to what was done with outbreaks of measles and polio and smallpox and other diseases.
Moderna to ask the FDA to greenlight its coronavirus vaccine|Carolyn Y. Johnson|November 30, 2020|Washington Post
It will then be about how they are used but a safe 90% efficacious vaccine is a game changer.
Infectious disease experts are very excited about the Pfizer and BioNTech vaccine|kdunn6|November 9, 2020|Fortune
The possibility that interferon may help some people is enticing because it appears most efficacious in the early stages of infection, when life-threatening respiratory failure could still be averted.
Covid-19 scientists flag key immune function as a turning point in life threatening cases|kdunn6|September 25, 2020|Fortune
The likelihood is that at least two, three, or four of those will probably prove to be both safe and efficacious.
When Bill Gates thinks we’ll have a COVID-19 vaccine—and why that won’t be the end of the pandemic|cleaf2013|September 21, 2020|Fortune

Beyond Mab Tabs, if an efficacious product can be made from plants and delivered in a modern form factor, we have it in our sights.
The founder of wellness startup Mab & Stoke on the growth of ‘pay what you can’ options during the pandemic|Rachel King|September 20, 2020|Fortune
Nothing has contributed so efficaciously, for some years past, to the progress of the native English drama.
The English Stage|Augustin Filon
And that this may be done more efficaciously and permanently the angels aid by their operation in it.
The Catholic World; Vol. IV.; October, 1866, to March, 1867.|E. Rameur
They are likewise interested in the maintenance of a powerful fleet by the Union, to protect them efficaciously.
American Institutions and Their Influence|Alexis de Tocqueville et al.
According to the doctors, soporific, injected into the human body by the de Pravaz syringe, acts violently and efficaciously.
Messengers of Evil|Pierre Souvestre
In malarial conditions there is nothing that acts so promptly and efficaciously as Sinkina.
The Propaganda for Reform in Proprietary Medicines, Vol. 1 of 2|Various

British Dictionary definitions for efficacious

efficacious

/ (ˌɛfɪˈkeɪʃəs) /

adjective

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

Derived forms of efficacious

efficaciously, adverbefficaciousness, noun

Word Origin for efficacious

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

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

efficacious

Origin of efficacious

OTHER WORDS FROM efficacious

Words related to efficacious

How to use efficacious in a sentence

British Dictionary definitions for efficacious

Derived forms of efficacious

Word Origin for efficacious