The figure below illustrates the different elements of a prism:
- The two parallel planes that cut the generatrices of a prismatic surface form two congruent polygons called the bases of the prism.
- Each of the two polygonal chains where the prismatic surface and the two parallel planes meet is called the directrix of the prism.
- The height of a prism is the distance between the two bases of a prism.
- The length of a right rectangular prism is the longest dimension of its base.
- A prism is a right prism when its generatrices are perpendicular to its bases; otherwise, it is an oblique prism.
A prism is named according to its bases:
- If the bases of a prism are squares, it is a square prism;
- If the bases of a prism are triangles, it is a triangular prism;
- If the bases of a prism are pentagons, it is a pentagonal prism;
- If the bases of a prism are hexagons, it is a hexagonal prism.
If the bases of a right prism are regular polygons, then the prism is a regular prism.
Many everyday objects have the shape of a prism: cereal box, tissue box, packaging box, filing cabinet, piece of cheese, building, etc.
Examples of prisms:
These polyhedra are not prisms: