Theorem rel0

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

	Ref	Expression
Assertion	rel0	$$⊢\mathrm{Rel}\varnothing$$

Proof

Step	Hyp	Ref	Expression
1		0ss	$$⊢\varnothing \subseteq \mathrm{V}\times \mathrm{V}$$
2		df-rel	$$⊢\mathrm{Rel}\varnothing \leftrightarrow \varnothing \subseteq \mathrm{V}\times \mathrm{V}$$
3	1 2	mpbir	$$⊢\mathrm{Rel}\varnothing$$