Board Thread:The Panopticon/@comment-188432-20140713043536/@comment-183721-20140713202750

And if there is no in-universe definition of the word "companion", now can you even create a template for companions? It's nothing more than bogus speculation on your part. Would you have us rename the templates to "associates" or "allies of the Doctor", since we can't even define "companion"? (Which might work, IMO)

I am not against using OOU material; I am just saying I do not find it sufficient or consistent. I feel we need some sort of consistent in-universe guideline or general inferences, or at the least some sort of authoritative DW reference book. In-universe inferences (even without having a definition), there are some factors that most companions have in common:
 * They travel with the Doctor in the TARDIS.
 * They are invited to travel in the TARDIS by the Doctor, or are allowed to travel in the TARDIS with him.