Theorem nnoni

Description: A natural number is an ordinal number. (Contributed by NM, 27-Jun-1994)

	Ref	Expression
Hypothesis	nnoni.1	|- A e. _om
Assertion	nnoni	|- A e. On

Proof

Step	Hyp	Ref	Expression
1		nnoni.1	|- A e. _om
2		nnon	|- ( A e. _om -> A e. On )
3	1 2	ax-mp	|- A e. On