Equivalence Relations
lA relation with the reflexive, symmetric, and transitive properties is called an equivalence relation. Such a relation generalizes the notion of equality, since in this case if x is related to z and y is related to z, then x is related to y.

In other words, if each of a set of elements is related to a common thing, the elements in the set and the common thing are all related to each other.

A
D
B
C
E
F
Equivalence: