Board Thread:The Reference Desk/@comment-7657843-20161112133450/@comment-20607870-20161112215438

I believe that a spin off is a fictitious continuation of the series. Such as SJA, TW, K9&C, K9, Mindgame, Auton, P.R.O.B.E. and Class. To name a few on screen ones.

DW Confidential and DW Extra are behind the scenes programmes, documentaries... I'd try to avoid using spin off but that's just me.