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90s Slang You Should Know


[ef-i-key-shuh s] /ˌɛf ɪˈkeɪ ʃəs/
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
1520-30; < Latin efficāci- (stem of efficāx) effectual. See efficient, -acious
Related forms
efficaciously, adverb
efficaciousness, noun
nonefficacious, adjective
nonefficaciously, adverb
unefficacious, adjective
unefficaciously, adverb Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2017.
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Examples from the Web for efficaciously
Historical Examples
  • Any generation that wants to can do well, but it must want to do efficaciously.

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

    Serge Panine, Complete Georges Ohnet
  • It covertly but most efficaciously undermined the customs which it pretended merely to interpret.

    Ancient Law Sir Henry James Sumner Maine
  • 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
  • This I hinted to L——, and his own susceptibility had hinted it to him efficaciously before I spoke.

    Leonora Maria Edgeworth
  • They also have waggons covered with black felt so efficaciously that no rain can enter.

    Some Heroes of Travel W. H. Davenport Adams
  • Nothing has contributed so efficaciously, for some years past, to the progress of the native English drama.

    The English Stage Augustin Filon
  • An indigent person who causes his child to be efficaciously vaccinated receives a present of three francs from the authorities.

    Old and New Paris, v. 2 Henry Sutherland Edwards
  • Ivan felt but little inconvenience from his wound; the aged Hagar having treated it so efficaciously.

    The Circassian Chief W.H.G. Kingston
British Dictionary definitions for efficaciously


capable of or successful in producing an intended result; effective as a means, remedy, etc
Derived Forms
efficaciously, adverb
efficaciousness, noun
Word Origin
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
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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.

Online Etymology Dictionary, © 2010 Douglas Harper
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