In abstract algebra, a **congruence relation** (or simply **congruence**) is an equivalence relation on an algebraic structure (such as a group, ring, or vector space) that is compatible with the structure in the sense that algebraic operations done with equivalent elements will yield equivalent elements.[1] Every congruence relation has a corresponding quotient structure, whose elements are the equivalence classes (or **congruence classes**) for the relation.[2]