Is it appropriate to address a PhD holder as "doctor" (without name)? In the US and Canada, I addressed my lecturers and instructors as &quot;Professor X&quot;, &quot;Dr. X&quot;, &quot;Mr. X&quot;, or &quot;Ms. X&quot; (depending on their formal education and academic position). I am currently at a university in Southeast Asia where students rarely (almost never) address university staff by name. They will say (always in English), &quot;thank you professor&quot;, &quot;thank you doctor&quot;, &quot;good morning sir&quot;, &quot;good morning miss&quot;, etc. There is nothing wrong with this; it's just the academic custom here.
My question is about US and Canadian academia: is it appropriate to address a PhD holder as &quot;doctor&quot; without name? For example, is it appropriate to say &quot;thank you doctor&quot; instead of &quot;thank you Dr. X&quot;? I recall hearing &quot;thank you professor&quot; (without name), but I can't recall hearing &quot;thank you doctor&quot; (without name).
In North American English, &quot;doctor&quot; without a name usually means a medical doctor.  To address a PhD or university instructor in that manner is neither appropriate nor inappropriate, but it is unusual.  &quot;Professor Lastname&quot; is a safe choice, but customs vary.