Having a certain order of complexity or being defined on a certain logical level (seetheory of logical types). A property, being defined within one variable or set is of ordinality one. A relation between two entities is of ordinality two, ..., a relation with n arguments is of ordinality n. A different convention of expressing ordinality is to count: unary relation or property, binary relation, ternary relation, quarternary relation,..., n-ary relation. A system within n variables contains up to n!/(m!(n-m)!) relations of ordinality m, msee structure,organization). (Krippendorff)