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efficacy

[ef-i-kuh-see] /ˈɛf ɪ kə si/
noun, plural efficacies.
1.
capacity for producing a desired result or effect; effectiveness:
a remedy of great efficacy.
Origin of efficacy
1520-1530
1520-30; < Latin efficācia, equivalent to efficāc- (see efficacious) + -ia -y3
Related forms
nonefficacy, noun
Dictionary.com Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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British Dictionary definitions for efficacy

efficacy

/ˈɛfɪkəsɪ/
noun
1.
the quality of being successful in producing an intended result; effectiveness
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 efficacy
n.

1520s, from Latin efficacia "efficacy, efficiency," from efficax (genitive efficacis) "powerful, effective," from stem of efficere "work out, accomplish" (see effect). Earlier in same sense was efficace (c.1200), from Old French eficace (14c.), from Latin efficacia; also efficacite (early 15c.), from Latin efficacitatem.

Online Etymology Dictionary, © 2010 Douglas Harper
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