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 of held a position that earned them the title.

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

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

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

River Song introduced herself to the Tenth Doctor as a professor of archaeology. (DW: Silence in the Library)