Dr. or Professor?

[Pacific.O]

When I officially write a prospective professor's name in the application form, which one do I have to choose?

Professor : professor/ associate professor (tenured) 

Dr. : associate professor (untenured)/ assistant professor/ research associate/ postdoc fellow...

Am I right?

[TakeruK]

The short answer is that it shouldn't really matter. 

The longer answer is that I'd personally use "Professor" instead of "Dr" as a title unless "Prof" is not the correct title.

And for the longest answer...

In my experience, I have never encountered a place in North America that uses a different title of address for tenured vs. untenured professors or for different professor ranks. If the person is a faculty member, use of "Professor" is okay. "Dr" is for postdocs and researchers who have a doctorate but are not a professor.

Note that it's possible to be a "Professor" without having a PhD. To me, "Professor" is more like a job title and it would be correct in some places to refer to someone teaching at a college by the title of "Professor" even if they do not have a doctorate (e.g. some colleges/junior colleges hire people with Masters degree to teach, or you might have a guest that is outside of academia teaching a course that they have expertise in). But these cases are likely not going to apply to the specific case you mention here.

[fuzzylogician]

I would use Professor for anyone who is a professor of any rank (assistant, associate, full), tenured or not, if approached for anything teaching related. Otherwise I would use Dr., including for postdocs and other folks with PhDs whose job description is not professor. But either way unless someone is incredibly picky, it shouldn't matter. A professor shouldn't get upset if you refer to them as Dr. so-and-so; they are a Dr. 

[rising_star]

If someone has a PhD, then "Dr." is the most respectful title to use in my book. Don't differentiate by rank.