Theorem rel0

Description: The empty set is a relation. (Contributed by NM, 26-Apr-1998)

	Ref	Expression
Assertion	rel0	⊢ Rel ∅

Proof

Step	Hyp	Ref	Expression
1		0ss	⊢ ∅ ⊆ ( V × V )
2		df-rel	⊢ ( Rel ∅ ↔ ∅ ⊆ ( V × V ) )
3	1 2	mpbir	⊢ Rel ∅