Similarly, R′ = {(a, b) : | a – b | ≥ 0} is the whole set A × A, as all pairs
(a, b) in A × A satisfy | a – b | ≥ 0 These two extreme examples lead us to the
following definitions Definition 1 A relation R in a set A is called empty relation, if no element of A is
related to any element of A, i e