S> A relation R on a Set A which iS a {partial ordering} i.e. it iS reflexive (xRx), tranSitive (xRyRz => xRz) and antiSymmetric (xRyRx => x=y) and for any two elementS x and y in A, either x R y or y R x. See alSo equivalence relation, well-ordered. (1995-02-16)