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Origin of inefficacy

From the Late Latin word inefficācia, dating back to 1605–15. See in-3, efficacy Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for inefficacy

Historical Examples of inefficacy

Word Origin and History for inefficacy

"want of force or virtue to produce the desired effect," 1610s, from Late Latin inefficacia, from inefficacem (nominative inefficax), from in- "not, opposite of" (see in- (1)) + efficax (see efficacy).

Online Etymology Dictionary, © 2010 Douglas Harper