complete lattice
Complete lattices
A complete lattice is a poset such that every subset of has both a supremum
and an infimum
in .
For a complete lattice ,the supremum of is denoted by ,and the infimum of is denoted by .Thus is a bounded lattice,with as its greatest element and as its least element.Moreover, is the infimum of the empty set
,and is the supremum of the empty set.
Generalizations
A countably complete lattice is a poset such that every countable subset of has both a supremum and an infimum in .
Let be an infinite cardinal.A -complete lattice is a lattice
such that for every subset with , both and exist.(Note that an -complete latticeis the same as a countably complete lattice.)
Every complete lattice is a for every infinite cardinal ,and in particular is a countably complete lattice.Every countably complete lattice is a bounded lattice.