Editing Glossary of order theory (section)

== W ==

* '''[[Way-below relation]]'''. In a poset ''P'', some element ''x'' is ''way below'' ''y'', written ''x''<<''y'', if for all directed subsets ''D'' of ''P'' which have a supremum, ''y'' ≤ ''sup D'' implies ''x'' ≤ ''d'' for some ''d'' in ''D''. One also says that ''x'' '''approximates''' ''y''. See also [[domain theory]].
* '''[[Weak order]]'''.  A partial order ≤ on a set ''X'' is a weak order provided that the poset (X, ≤) is [[isomorphic]] to a countable collection of sets ordered by comparison of [[cardinality]].