LatticE

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.