An acoptic polyhedron is a polyhedron with simple polygons as faces and no self-intersections, so that its surface is an embedded 2-manifold (Grünbaum 1999). The word "coptic" derives from the Greek for "to cut."
Acoptic polyhedra need not have the topology of a sphere. In particular, they include toroidal polyhedra, such as the Császár polyhedron (Grünbaum 1999). The term therefore has broader scope than the geometric meaning of simple polyhedron, which requires the solid to be homeomorphic to a closed ball. It also does not impose the three-face condition at each polyhedron vertex used in the combinatorial definition of a simple polyhedron.
