Theorem 6on

Description: Ordinal 6 is an ordinal number. (Contributed by BTernaryTau, 4-Sep-2026)

	Ref	Expression
Assertion	6on	⊢ 6o ∈ On

Proof

Step	Hyp	Ref	Expression
1		df-6o	⊢ 6o = suc 5o
2		5on	⊢ 5o ∈ On
3	2	onsuci	⊢ suc 5o ∈ On
4	1 3	eqeltri	⊢ 6o ∈ On