A
polyhedron where all vertices lie in two parallel planes. Under some circumstances I forget it is called a
prismoid. Some particular families of prismatoids:
- Prisms, where the polygons in each plane are congruent and joined by rectangles or pallelograms;
- Antiprisms, where the polygons in each plane are congruent and joined by an alternating strip of triangles;
- Frustrums[?], where the polygons are similar and joined by trapezoids;
- Pyramids, where one plane contains only a single point;
- Cupolas, where the polygon in one plane contains twice as many points as the other and is joined to it by alternating triangles and rectangles.