A pyramid is a solid that has the following characteristics. It has one base, which is a polygon. The vertices of the base are each joined to a point, not in the plane of the base. This point is called the vertex of the pyramid. The triangular sides, all of which meet at the vertex, are its lateral faces. The segments where the lateral faces intersect are lateral edges. The perpendicular segment from the vertex to the plane of the base is the altitude of the pyramid.