User blog comment:Syst3ms/A formal definition for UNOCF/@comment-35470197-20180728080043/@comment-35392788-20180728084228

Cofinality has its usual definition, i.e "length of fundamental sequence".

So, cof(0) = 0, cof(a+1) = 1, cof(Ω_(a+1)) = Ω_(a+1), etc.