Hermit

Hermits were individuals who lived on their own.
The young First Doctor would play truant so that he could visit the Hermit, who lived near him. (PROSE: The Eight Doctors) The Third Doctor once told Jo Grant about his home: "When I was a little boy, we used to live in a house that was perched halfway up the top of a mountain. Behind our house, there sat under a tree an old man. A hermit, a monk. He'd lived under this tree for half his lifetime, so they said, and had learned the secret of life. So, when my black day came, I went and asked him to help me." (TV: The Time Monster) The Third Doctor also told Alistair Lethbridge-Stewart about what he had learned from the hermit: "I spent some of the finest hours of my life with that old man. It was from him I first learned how to look into my mind." (TV: Planet of the Spiders)
The Fourth Doctor similarly told Romana II about the old hermit he know who came from the mountains of South Gallifrey, who told him of the Record of Rassilon. (TV: State of Decay) Thessalia knew that many hermits lived in the southern mountains of the Homeworld. (PROSE: The Return of the King)
The Sixth Doctor, confused by his fresh regeneration, decided to become a hermit and bring his companion Peri Brown with him, as his disciple and servant. The asteroid Titan III was the supposed hermitage. Soon, he cleared up his mind. (TV: The Twin Dilemma)
A member of the Celestial Intervention Agency who later joined the Celestis as an Investigator became a hermit in Mictlan. (PROSE: The Taking of Planet 5)
The Tenth Doctor told Professor Yana that he was a "bit of a hermit." Pointing out Martha and Jack, Yana replied, "A hermit... with friends?" to which the Doctor replied that they were "Hermits United" who met up every ten years to discuss caves. (TV: Utopia)