Full Idea
A binary relation in a set is a 'partial ordering' just in case it is reflexive, antisymmetric and transitive.
Gist of Idea
A 'partial ordering' is reflexive, antisymmetric and transitive
Source
José L. Zalabardo (Introduction to the Theory of Logic [2000], §1.6)
Book Reference
Zalabardo,José L.: 'Introduction to the Theory of Logic' [Westview 2000], p.23