efficacious

American  

[ef-i-key-shuhs] / ˌɛf ɪˈkeɪ ʃəs /

adjective

1. 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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efficacious British  

/ ˌɛfɪˈkeɪʃəs /

adjective

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

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Usage

What are other ways to say efficacious? The adjective efficacious describes things that are capable of having the desired result or effect. But efficacious isn’t quite the same as effectual, effective, or efficient! Find out why on Thesaurus.com. 

Other Word Forms

Derived Forms

• unefficaciously
  adverb
• unefficacious
  adjective
• nonefficaciously
  adverb
• efficaciously
  adverb
• efficaciousness
  noun
• nonefficacious
  adjective

Etymology

Origin of efficacious

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

Explanation

When you really want to do something right, really nail it, really get at what you were going for — you're trying to be efficacious, or produce the effect you intended. The word efficacious is made up of the Latin efficere meaning "accomplish" and the suffix -ious meaning "full of." Something that's efficacious is full of accomplishment. An efficacious medicine is one that cures you of the ailment you had. An efficacious recipe is one that comes out the way you intended it to taste. Remember that efficacious has two fs and two cs in it and you'll be efficacious in your spelling of the word.

Example Sentences

"Efficacious?" a raffish physician is quoted in the Journal.

From Slate • May 3, 2013

Efficacious, ef-fi-kā′shus, adj. able to produce the result intended.—adv.

From Chambers's Twentieth Century Dictionary (part 2 of 4: E-M) by Various

Efficacious petitions 4:3 What we most need is the prayer of fervent desire         for growth in grace, expressed in patience, meekness,         love, and good deeds.

From Science and Health, with Key to the Scriptures by Eddy, Mary Baker

Efficacious as the Christian religion has been to destroy or mitigate evil, it has failed to render the so-called Christian slaveholder better than the pagan, or to improve the condition of the bondsmen.

From Slavery and Four Years of War, Vol. 1-2 A Political History of Slavery in the United States Together With a Narrative of the Campaigns and Battles of the Civil War In Which the Author Took Part: 1861-1865 by Keifer, Joseph Warren

Efficacious enim et plus movent, quae in oculos quam quae in aures incidunt.

From The Works of Mr. George Gillespie (Vol. 1 of 2) by Gillespie, George