A relation R on a set A is said to be an equivalence relation on A iff:

1. Its reflexive i.e (a,a) ∈ R ∀ a ∈ A

2. Its symmetric i.e (a,b) ∈ R → (b,a) ∈ R ∀ a,b ∈ A

3. Its transitive i.e (a,b) ∈ R and (b,c) ∈ R → (a,c) ∈ R ∀

a,b,c ∈ A