2.2 Binary relations Definition 2.5: Let A and B be sets. a binary relation from a to B is a subset of AXB. a relation on A is a relation from a to 4. f (a,bER, we say that a is related to b by R, we also write aR 6. If(a,b)eR, we say that a is not related to b by r, we also write a L b we say that empty set is an empty relation.2.2 Binary relations Definition 2.5: Let A and B be sets. A binary relation from A to B is a subset of A×B. A relation on A is a relation from A to A. If (a,b)R, we say that a is related to b by R, we also write a R b. If (a,b)R , we say that a is not related to b by R, we also write a ℟ b. we say that empty set is an empty relation