  We define toric partial orders, corresponding to regions of graphic toric
hyperplane arrangements, just as ordinary partial orders correspond to regions
of graphic hyperplane arrangements. Combinatorially, toric posets correspond to
finite posets under the equivalence relation generated by converting minimal
elements into maximal elements, or sources into sinks. We derive toric
analogues for several features of ordinary partial orders, such as chains,
antichains, transitivity, Hasse diagrams, linear extensions, and total orders.
