What is the difference between “affirm” and “acknowledged”?
&quot;Acknowledged&quot; means I heard you &amp; understood what you said &amp; I take responsibility for the information you just gave me.
&quot;Affirm&quot; and its opposite, &quot;negative,&quot; are answers to a yes/no question.
They aren't really interchangeable, although Hollywood script writers are notorious for getting details like that wrong.
An example of correct usage would be, &quot;Callsign 123, is your ride smooth at FL350?&quot; &quot;Callsign 123, affirm.&quot; (Answers the question, yes the ride here is smooth.&quot;) Then, &quot;Callsign 123, we've had reports of light turbulence at your 12 o'clock and 100 miles.&quot; &quot;Callsign 123, acknowledged.&quot; (Or, &quot;roger&quot; is more common, but same meaning... either way, I've received &amp; understood the turbulence report.)
To reply &quot;roger&quot; or &quot;acknowledged&quot; to the question &quot;is your ride smooth&quot; is incorrect, because all you'd be saying is, I heard your question. There isn't any &quot;yes&quot; or &quot;no&quot; component to either of those replies. Likewise, to reply &quot;affirm&quot; to the &quot;turbulence ahead&quot; call is wrong because there was no question being asked there. The controller just needs to know that you heard the information so that it doesn't have to be repeated.
Interestingly, the FAA Pilot-Controller Glossary doesn't list &quot;acknowledged&quot; at all, but lists &quot;acknowledge&quot; as a directive: tell me that you heard me.
It also lists &quot;affirmative&quot; and not &quot;affirm&quot; -- that may be more used elsewhere. Also, with the quality of modern radios, the risk of the initial syllable(s) getting lost &amp; the receiver left puzzling over &quot;...ative&quot; has probably diminished over time.