In Boolean algebra (structure), the inclusion relation is defined as and is the Boolean analogue to the subset relation in set theory. Inclusion is a partial order.
The inclusion relation can be expressed in many ways:
The inclusion relation has a natural interpretation in various Boolean algebras: in the subset algebra, the subset relation; in arithmetic Boolean algebra, divisibility; in the algebra of propositions, material implication; in the two-element algebra, the set { (0,0), (0,1), (1,1) }.