Partially ordered set: Difference between revisions

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* For a set ''X'' and a partially ordered set ''P'', the [[function space]] containing all functions from ''X'' to ''P'', where {{nowrap|''f'' ≤ ''g''}} if and only if {{nowrap|''f''(''x'') ≤ ''g''(''x'')}} for all <math>x \in X.</math>
* A [[Fence (mathematics)|fence]], a partially ordered set defined by an alternating sequence of order relations {{nowrap|''a'' < ''b'' > ''c'' < ''d'' ...}}
* The set of events in [[special relativity]] and, in most cases,{{efn|See ''{{slink|General relativity#Time travel}}''.}} [[general relativity]], where for two events ''X'' and ''Y'', {{nowrap|''X'' ≤ ''Y''}} if and only if ''Y'' is in the future [[light cone]] of ''X''. An event ''Y'' can only be causally affected by ''X'' only if {{nowrap|''X'' ≤ ''Y''}}.
 
One familiar example of a partially ordered set is a collection of people ordered by [[genealogy|genealogical]] descendancy. Some pairs of people bear the descendant-ancestor relationship, but other pairs of people are incomparable, with neither being a descendant of the other.