Reincarnation

Reincarnation was a religious belief. The Aztecs believed Barbara Wright to be a reincarnation of Yetaxa. (TV: The Aztecs)

Buddhists believed in reincarnation, specifically that they will be reborn over and over again until they are free from suffering and obtain Nirvana. (AUDIO: The Natural History of Fear)

After his encounter with The Book of the Old Time, the Seventh Doctor began to suspect that before regeneration, there had been reincarnation. (PROSE: Cat's Cradle: Time's Crucible) The Doctor later discovered that he might be the genetic reincarnation of the Other. (PROSE: Lungbarrow)