Professor

Professor was a title given to scholarly teachers to denote their academic ability. It was often, though not exclusively, given to those who had achieved a certain level of learning or held a position that earned them the title.

Ace often referred to the Seventh Doctor as "the Professor" throughout her early association with him (TV: Dragonfire, et. al.) and still continued to refer to him as "professor" in a friendly manner several years later. (PROSE: Happy Endings)

References

In the year 100,000,000,000,000, Yana used the title of professor, despite there having been no universities for over a century. (TV: Utopia)

Professor Marius, who built K9 and later gave him to the Fourth Doctor, was a specialist in extraterrestrial pathological endomorphisms (alien viruses) at the Bi-Al Foundation in the year 5000. (TV: The Invisible Enemy)

Bernice Summerfield originally faked her qualifications as a professor of archaeology; however, she did eventually obtain a professorship. (PROSE: Love and War, Return of the Living Dad)

Professor Candy interviewed River Song when she applied to Luna University to study archaeology. (TV: Let's Kill Hitler)

River Song introduced herself to the Tenth Doctor as a professor of archaeology. (TV: Silence in the Library) She was not yet a professor at the time of the crash of the Byzantium, although the Eleventh Doctor accidentally let slip that she one day would be. (TV: The Time of Angels) She was forced to "kill" the Doctor almost immediately after receiving her doctorate. (TV: Closing Time) After she was pardoned for his "murder," she returned to Archaeology and became a Professor. (TV: The Angels Take Manhattan)

The crew of the Russian submarine that the Eleventh Doctor encountered in 1983 called Grisenko "the Professor". (TV: Cold War)

K'rokk was a professor. (COMIC: The Cornucopia Caper)