Theorem 7on

Description: Ordinal 7 is an ordinal number. (Contributed by BTernaryTau, 4-Sep-2026)

	Ref	Expression
Assertion	7on	⊢ 7o ∈ On

Proof

Step	Hyp	Ref	Expression
1		df-7o	⊢ 7o = suc 6o
2		6on	⊢ 6o ∈ On
3	2	onsuci	⊢ suc 6o ∈ On
4	1 3	eqeltri	⊢ 7o ∈ On