Incarnation

An incarnation was the term applied to the bodies/selves/lives of a Time Lord. While it was sometimes used interchangeably with "regeneration", (TV: The Keeper of Traken) incarnations were actually the result of this process, with Time Lords regenerating from one incarnation to another. Barring special circumstances, a Time Lord could only have thirteen incarnations, (TV: The Deadly Assassin) before their symbiotic nuclei started to break down. (AUDIO: Trial of the Valeyard) Some, like the Master and the Doctor, have been given new regeneration cycles, bybassing this limit.

Looking back on his previous lives, the Doctor occasionally used the word incarnation. (TV: The Twin Dilemma, AUDIO: The Light at the End, The Chimes of Midnight, Dead London, Scaredy Cat) He also used it in reference to the Master, (TV: Doctor Who) and others used it to talk about the Doctor's regenerations, as well. According to the Master, the Valeyard came from between the Doctor's twelfth and final incarnations. (TV: The Ultimate Foe)

The Eleventh Doctor thought he had never used the word incarnation in that capacity, but was proven wrong by Ally, from an alternate dimension, who played a clip from Doctor Who of the Sixth Doctor discussing his "last incarnation" in The Twin Dilemma. He conceded, but claimed that the word was hardly ever used. (COMIC: The Girl Who Loved Doctor Who)