User blog comment:Deedlit11/Ordinal notations II: Up to the Bachmann-Howard ordinal/@comment-5150073-20130628190935/@comment-1605058-20130628191637

For infinite limit ordinal a, cofinality is size of smallest set of ordinals with a as upper bound. Cofinality of 0 is 0, and cofinality of succesor ordinal is 1.