• synonyms


[ef-i-key-shuh s]
See more synonyms for efficacious on Thesaurus.com
  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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Origin of efficacious

1520–30; < Latin efficāci- (stem of efficāx) effectual. See efficient, -acious
Related formsef·fi·ca·cious·ly, adverbef·fi·ca·cious·ness, nounnon·ef·fi·ca·cious, adjectivenon·ef·fi·ca·cious·ly, adverbun·ef·fi·ca·cious, adjectiveun·ef·fi·ca·cious·ly, adverb
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Related Words for efficaciously

finally, forcefully, completely, definitely, energetically, adequately, dramatically, productively, efficaciously, excellently, conclusively, capably, cogently, effectually, expertly, persuasively, tellingly

Examples from the Web for efficaciously

Historical Examples of efficaciously

  • Only one here can tell him efficaciously what he must hear, and that is Cayrol.

    Serge Panine, Complete

    Georges Ohnet

  • Yet small as are the variations, they act most efficaciously on certain minds.

  • He learns to manage his genius more prudently and efficaciously.

    Biographia Literaria

    Samuel Taylor Coleridge

  • Any generation that wants to can do well, but it must want to do efficaciously.

  • This I hinted to L——, and his own susceptibility had hinted it to him efficaciously before I spoke.


    Maria Edgeworth

British Dictionary definitions for efficaciously


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

Word Origin and History for efficaciously



"sure to have the desired effect" (often of medicines), 1520s, from Latin efficaci-, stem of efficax (see efficacy) + -ous. Related: Efficaciously; efficaciousness.

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Online Etymology Dictionary, © 2010 Douglas Harper