I usually use the word "effectiveness" in conversation, but sometimes I use the word "efficacy" then self-correct with "effectiveness" . Is there a practical difference between them?
Learn English – What’s the difference between “efficacy” and “effectiveness”
connotationderivational-morphologydifferencesmeaningsuffixes
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Best Answer
For all practical purposes, I don't think there's any difference in meaning between efficacy and effectiveness - or indeed efficaciousness, come to that.
My own feeling is that efficacy is somewhat stilted - pompous, even, despite the fact that it's a shorter word...maybe people like to use efficacy because it sounds more scientific. Possibly my perception is influenced by the fact that effectiveness has been the more common version for the past century...
Here a link that notes the difference: http://www.ahrq.gov/clinic/tp/efftrialtp.htm...Note "to distinguish effectiveness (pragmatic) from efficacy (explanatory) trials " Also, more at wikipedia.
However, based on past experience with hearing the word in scientific contexts, I googled efficacy and found that "In medicine, it is the ability of an intervention or drug to reproduce a desired effect in expert hands and under ideal circumstances." I guess that distinguishes it from effectiveness in practical real-world application. I know that one company I worked for conducted both "efficacy trials" and "field trials" for its products.