An algebra is congruence distributive (or CD for short) if its lattice of congruence relations is a distributive lattice.

A class of algebras is congruence distributive if each of its members is congruence distributive.

Congruence distributivity has many structural consequences. The most striking one is perhaps Jónsson's Lemma ¹⁾ which implies that a finitely generated CD variety is residually finite.

Equationally def. pr. cong.

Congruence modular