The truth-functional relationship which obtains between any two propositions having the same truth value (either both true or both false); a case in which such a relationship exists.
Origin
Late 19th century; earliest use found in Mind.
Definition of material equivalence in US English:
material equivalence
noun
Logic
The truth-functional relationship which obtains between any two propositions having the same truth value (either both true or both false); a case in which such a relationship exists.