Wikipedia 10K Redux by Reagle from Starling archive. Bugs abound!!!
A lattice is a set L, together with two binary operations v,^, such that for any a,b,c in L, ava=a a^a=a (idempotency laws) avb=bva a^b=b^a (commutativity laws) av(bvc)=(avb)vc a^(b^c)=(a^b)^c (associativity laws) av(a^b)=a a^(bvc)=a (absorption laws) If avb=b, or equivalently a^b=a, we say that a<=b. Thus defined, <= forms a PartialOrder on L, and moreover (L,v,^) is the unique lattice associated therewith. TotalOrderedSet''s'' and BooleanAlgebra''e'' are two important types of lattice.