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Reflexive relation R in X is a relation with (a, a) ∈ R ∀ a ∈ X ®
Symmetric relation R in X is a relation satisfying (a, b) ∈ R implies (b, a) ∈ R ®
Transitive relation R in X is a relation satisfying (a, b) ∈ R and (b, c) ∈ R
implies that (a, c) ∈ R ®
Equivalence relation R in X is a relation which is reflexive, symmetric and
transitive