PARTIALLY ORDERED SET
Definition
An object is a <PARTIALLY ORDERED SET> if and only if: it is a <STRUCTURE(math)>; it contains: a principal set S; an order Z, which is a set of pairs of members of S, such that: for all x and y in S, if (x, y) is a member of Z, then (y, x) is not a member of Z; for all x in S, (x, x) is not a member of Z; for all x, y and z in S, if (x, y) and (y, z) are members of Z, then (x, z) is also a member of Z