Ok, I see. Now it makes sense.
Ok, I agree on that formulating.
I have a book in geometry defines a convex polyhedron as following (which means that there are non convex polyhedra as you said):
(I do not understand the underlined part). I think, we can say that each hyperplane is cut by two other hyperplanes to form a polytope. This process makes a polytope intersected polygons, and a polygon is bounded, and its edges are line segments. Am I right on this?