Companions means: Doctor Who’s companions have all been chosen by him to go on their own journeys. Each Doctor had at least one companion, up to 101 in total, over the course of 4 seasons. Rose is the Doctor’s final companion. She has a full-fledged life story, which the Doctors get to read from Rose’s debut story. She is not cut off from the people and places she loved, as other companions are. (in Community Dictionary, added by Gavin Dawson)