Regeneration is an ability possessed by the Doctor.
In the long running British science fiction television series Doctor Who , regeneration is a biological ability exhibited by the Time Lords , a race of fictional humanoids originating on the planet Gallifrey . The Doctor (Doctor Who) . The transition to each succeeding actor is explained within the show 's narrative through the plot device of `` regeneration '' , a biological function of his race that allows their change of cellular structure and appearance with recovery following a potentially fatal injury . The War Doctor and an aborted regeneration are counted in his previous cycle of twelve regenerations .