Doctor

Doctor was a title used by physicians and the holders of certain advanced university degrees. According to River Song, the word came from the renegade Time Lord known as the Doctor. (TV: A Good Man Goes to War) The Doctor himself seemed to concur with this claim; the Fourth Doctor told Harry Sullivan "You may be a doctor. But I am the Doctor. The definite article, you might say." (TV: Robot) The Twelfth Doctor likewise clarified to Grant that he was the Doctor and that he "started it", claiming himself to be "The one. The main one, the original.", he went on to say that all other doctors were "based on [him]" and "now everyone who wants to sound clever calls themselves doctor." (TV: The Return of Doctor Mysterio) The First Doctor also claimed to be the original doctor upon hearing his twelfth incarnation call himself "the Doctor". (TV: The Doctor Falls)

While the term originally and typically meant "healer" or "wise man", some cultures by the 52nd century used the word to mean "great warrior" due to their fear of the Doctor. It was implied that the word's true origin had been forgotten. (TV: A Good Man Goes to War) The Eleventh Doctor considered the title to mean "total, screaming genius" and "modest and a tiny bit sexy." (TV: Asylum of the Daleks) In the 21st century, the title could be mistaken for the moniker of a drug dealer. (TV: The Lodger) While Dr Solow mentioned in 2084 that her training as a doctor meant that murder did not come easy to her, (TV: Warriors of the Deep) by the 45th century, to behave like a doctor was to kill people. (AUDIO: Plague of the Daleks)

In fact, the title originally meant to the Doctor that they were upholding their promise to "Never [be] cruel or cowardly; never give up, never give in." (TV: The Day of the Doctor) The Eighth Doctor liked to believe that being called "Doctor" meant he was a good man, and the War Doctor decided he was "Doctor no more" when he broke this promise, intending to join the Last Great Time War. (TV: The Night of the Doctor)

General Staal of the Tenth Sontaran Battle Fleet recognised "doctor" as the name of the "facechanger" and enemy of the Sontarans who led the battle in the Last Great Time War. (TV: The Sontaran Stratagem)

Occupation
A GP was a kind of doctor. Dr Melton was a GP. (AUDIO: A Mother's Son)

Academic distinction
to be added

The Doctor as a medical doctor
When asked by Polly Wright if his name implied he was a medical doctor, the Second Doctor claimed he graduated in Medicine in 1888 in Glasgow, (TV: The Moonbase) though Clara Oswald would later explain that he graduated in the wrong century. (TV: Death in Heaven) On other occasions, the Doctor's first, (TV: "The Forest of Fear", "Mighty Kublai Khan") second, (TV: The Krotons) fourth, (TV: The Ark in Space, PROSE: Sarah Jane and the Temple of Eyes) and fifth incarnations claimed not to be a doctor of medicine. (AUDIO: Red Dawn)

The Thirteenth Doctor identified herself as a doctor of medicine, science, engineering, candy floss, LEGO, philosophy, music, problems, people and hope, but mostly hope. (TV: The Tsuranga Conundrum) She claimed to have obtained a doctorate at the University of Gallifrey. (COMIC: Herald of Madness) The Eleventh Doctor confirmed that he was both a doctor of medicine and of cheesemaking. (TV: The God Complex)

The Fourth Doctor simply said he was a doctor of "many things", (TV: Revenge of the Cybermen) or "just about everything", placing emphasis on "just about". (AUDIO: The Darkness of Glass) The First Doctor claimed to be a "doctor of science". (TV: The Massacre) When questioned, the Sixth Doctor replied that he was a doctor of "this and that, mostly that". (AUDIO: The Spectre of Lanyon Moor) The Tenth Doctor introduced himself as a doctor "of everything" on Silo 16, leading Professor Yana to recognise him as a fellow scientist. (TV: Utopia)

Despite all this, the Doctor has shown medical knowledge on several occasions. (TV: World War Three, The Doctor Dances, New Earth, The Age of Steel, Smith and Jones, The Shakespeare Code, Planet of the Ood, The Poison Sky, The Unicorn and the Wasp, The Vampires of Venice, et al.)

In several circumstances, the Doctor let others think their title was to be intended as a physician. mentioned the Doctor's title as being "the man who makes people better". (TV: The Sound of Drums) The Doctor, in various incarnations, was known to assure people, "It's alright, I'm a doctor." (TV: Meglos, Ghost Light, The Shakespeare Code, Vincent and the Doctor, Knock Knock)

First Doctor

 * With the pirate Cherub and his party, who called him "Sawbones" — seaman's slang for a ship's doctor. (TV: The Smugglers)

Second Doctor

 * With Kirsty McLaren and her sick father, in Scotland, in 1746. (TV: The Highlanders)
 * To enter and rummage the Medical Centre of the Gatwick Airport, in 1966, along with the fake patient Jamie McCrimmon. (TV: The Faceless Ones)

Third Doctor

 * When mistaken for a medical doctor by Claire Forest who was expecting one to visit and take care of Martin Chisom. (AUDIO: Lost in the Wakefield Triangle)

Eleventh Doctor

 * When asked if he was a medical doctor and not just someone with a doctorate in cheesemaking, he replied that he was both. (TV: The God Complex)

Thirteenth Doctor

 * The Thirteenth Doctor claimed to have obtained her doctorate at the University of Gallifrey. (COMIC: Herald of Madness)

Behind the scenes

 * The idea that the word "doctor" derives from the Doctor was first advanced by Steven Moffat in a Usenet post in 1995.