Prism (geometry)
Solid with 2 parallel ''n''-gonal bases connected by ''n'' parallelograms / From Wikipedia, the free encyclopedia
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In geometry, a prism is a polyhedron comprising an n-sided polygon base, a second base which is a translated copy (rigidly moved without rotation) of the first, and n other faces, necessarily all parallelograms, joining corresponding sides of the two bases. All cross-sections parallel to the bases are translations of the bases. Prisms are named after their bases, e.g. a prism with a pentagonal base is called a pentagonal prism. Prisms are a subclass of prismatoids.
| Set of uniform n-gonal prisms | |
|---|---|
 Example: uniform hexagonal prism (n = 6) | |
| Type | uniform in the sense of semiregular polyhedron |
| Faces |
|
| Edges | 3n |
| Vertices | 2n |
| Vertex configuration | 4.4.n |
| Schläfli symbol | {n}×{ } [1] t{2,n} |
| Conway notation | Pn |
| Coxeter diagram |     |
| Symmetry group | Dnh, [n,2], (*n22), order 4n |
| Rotation group | Dn, [n,2]+, (n22), order 2n |
| Dual polyhedron | convex dual-uniform n-gonal bipyramid |
| Properties | convex, regular polygon faces, isogonal, translated bases, sides ⊥ bases |
| Net | |
 | |
| Example: net of uniform enneagonal prism (n = 9) | |
Like many basic geometric terms, the word prism (from Greek πρίσμα (prisma) 'something sawed') was first used in Euclid's Elements. Euclid defined the term in Book XI as “a solid figure contained by two opposite, equal and parallel planes, while the rest are parallelograms”. However, this definition has been criticized for not being specific enough in relation to the nature of the bases, which caused confusion among later geometry writers.[2][3]