Prisms and Pyramids
Polyhedra are not limited to the specifically designed platonic and archimedian solids. There are many more loosely defined polyhedra. Two of these are Prisms and Pyramids.
A pyramid is defined as a polyhedra that consists of a polygon where all of the corners are connected to another point that is not on the same plane as the polygon. Notice that the point doesn't have to be directly above the polygon it can be anywhere. Pyramids like this are known as Oblique Pyramids.