Metamath Proof Explorer

Theorem relssr

Description: The subset relation is a relation. (Contributed by Peter Mazsa, 1-Aug-2019)

Ref Expression
Assertion relssr 
|- Rel _S

Proof

Step Hyp Ref Expression
1 df-ssr 
 |-  _S = { <. x , y >. | x C_ y }
2 1 relopabiv 
 |-  Rel _S