And its ordinalitiy is also 0. Standard construction of ordinals is that each ordinal is the set of all its predecessors. (0 has no predecessors , hence 0 is t

And its ordinalitiy is also 0. Standard construction of ordinals is that each ordinal is the set of all its predecessors. (0 has no predecessors , hence 0 is the empty set.) (And so finite ordinals have the same ordinaliity as cardinality).