Pain

Pain was an unpleasant feeling experienced by organic beings in response to a stimulus that damaged the body in some way. (TV: The Gunfighters) Pain was often accompanied by autonomic responses. (AUDIO: The Movellan Grave) Pain could also be an emotional thing, as people feel pain when enduring Tragedy.

Certain parts of the humanoid body were more sensitive to pain than others, such as immediately below the eye. The pain of a cigarette being extinguished in this part of the body was enough to successfully break the Eighth Doctor's self-induced trance. (PROSE: Endgame)

The Eternal of the same name was a personification of the concept. (PROSE: Set Piece)

While pain was generally considered unpleasant, to the point of the word "pain" being used generally to describe an unpleasant experience or person, (TV: The Caves of Androzani) and as such was often treated with painkillers, (TV: Exit Wounds) some enjoyed the sensation of pain, while still others enjoyed pretending to be in pain. (PROSE: Of the City of the Saved...) In a more abstract sense, the Twelfth Doctor believed pain to be "a gift", because "without [pain], we can't feel the hurt we inflict". (TV: Death in Heaven) Additionally, some cultures did not show as much care for those in pain. When a Patient complained of pain, a Mondasian nurse responded simply by turning its volume down. (TV: World Enough and Time) Ironically, however, the Cybermen spoke extremely negatively of pain and spoke almost pityingly of unconverted individuals for still having the capacity for it. (TV: The Age of Steel)

The Monks believed that pain was information. (TV: Extremis)