An algebraic structure, such as a Boolean algebra, in which there are two dyadic operations that are both commutative and associative and satisfy the absorption and idempotent laws. The two dyadic operators, denoted by ∧ and ∨, are called the meet and the join respectively.
An alternative but equivalent view of a lattice is as a set L on which there is a partial ordering defined. Further, every pair of elements has both a greatest lower bound and a least upper bound. The least upper bound of {x,y} can be denoted by x ∨ y and is referred to as the join of x and y. The greatest lower bound can be denoted by x ∧ y and is called the meet of x and y. It can then be shown that these operations satisfy the properties mentioned in the earlier definition, since a partial ordering ≤ can be introduced by defining
Lattices in the form of Boolean algebras play a very important role in much of the theory and mathematical ideas underlying computer science. Lattices are also basic to much of the approximation theory underlying the ideas of denotational semantics.