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Uniform polyhedron
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A uniform polyhedron is a polyhedron which has regular polygons as faces and is transitive on its vertices (i.e. there is an isometry mapping any vertex onto any other). It follows that all vertices are congruent, and the polyhedron has a high degree of reflectional and rotational symmetry.
Uniform polyhedra may be regular, quasi-regular or semi-regular. The faces and vertices need not be convex, so many of the uniform polyhedra are also star polyhedra.
Excluding the infinite sets, there are 75 uniform polyhedra (or 76 if edges are allowed to coincide).
Categories include:
They can also be grouped by their symmetry group, which is done below.
blished the list of uniform polyhedra.
proved their conjecture that the list was complete.
independently proved the completeness, and showed that if the definition of uniform polyhedron is relaxed to allow edges to coincide then there is just one extra possibility.
numbering schemes for the uniform polyhedra are in common use, distinguished by letters:
>
Convex forms by Wythoff construction The convex uniform polyhedra can be named by Wythoff construction operations and can be named in relation to the regular form.
In more detail the convex uniform polyhedron are given below by their Wythoff construction within each symmetry group.
Within the Wythoff construction, there are repetitions created by lower symmetry forms. The cube is a regular polyhedron, and a square prism.

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Encyclopedia
A uniform polyhedron is a polyhedron which has regular polygons as faces and is transitive on its vertices (i.e. there is an isometry mapping any vertex onto any other). It follows that all vertices are congruent, and the polyhedron has a high degree of reflectional and rotational symmetry.
Uniform polyhedra may be regular, quasi-regular or semi-regular. The faces and vertices need not be convex, so many of the uniform polyhedra are also star polyhedra.
Excluding the infinite sets, there are 75 uniform polyhedra (or 76 if edges are allowed to coincide).
Categories include:
They can also be grouped by their symmetry group, which is done below.
History
- The Platonic solids date back to the classical Greeks and were studied by Plato, Theaetetus and Euclid.
- Johannes Kepler (1571-1630) was the first to publish the complete list of Archimedean solids after the original work of Archimedes was lost.
- Kepler (1619) discovered two of the regular Kepler-Poinsot polyhedra and Louis Poinsot (1809) discovered the other two.
- Of the remaining 66, Albert Badoureau (1881) discovered 37. Edmund Hess (1878) discovered 2 more and Pitsch (1881) independently discovered 18, of which 15 had not previously been discovered.
- The geometer Donald Coxeter discovered the remaining twelve in collaboration with J. C. P. Miller (1930-1932) but did not publish. M.S. and H.C. Longuet-Higgins and independently discovered 11 of these.
published the list of uniform polyhedra.
proved their conjecture that the list was complete.
- In 1974, Magnus Wenninger published his book Polyhedron models, which lists all 75 nonprismatic uniform polyhedra, with many previously unpublished names given to them by Norman Johnson.
independently proved the completeness, and showed that if the definition of uniform polyhedron is relaxed to allow edges to coincide then there is just one extra possibility.
- In 1993, Zvi Har'El produced a complete kaleidoscopic construction of the uniform polyhedra and duals with a computer program called Kaleido, and summarized in a paper Uniform Solution for Uniform Polyhedra, counting figures 1-80.
- Also in 1993, R. Mäder ported this Kaleido solution to Mathematica with a slightly different indexing system.
- In 2002 Peter W. Messer discovered a minimal set of closed-form expressions for determining the main combinatorial and metrical quantities of any uniform polyhedron (and its dual) given only its Wythoff symbol.
Indexing
Four numbering schemes for the uniform polyhedra are in common use, distinguished by letters:
- [C] Coxeter et al., 1954, showed the convex forms as figures 15 through 32; three prismatic forms, figures 33–35; and the nonconvex forms, figures 36–92.
- [W] Wenninger, 1974, has 119 figures: 1-5 for the Platonic solids, 6-18 for the Archimedean solids, 19-66 for stellated forms including the 4 regular nonconvex polyhedra, and ended with 67-119 for the nonconvex uniform polyhedra.
- [K] Kaleido, 1993: The 80 figures were grouped by symmetry: 1-5 as representatives of the infinite families of prismatic forms with dihedral symmetry, 6-9 with tetrahedral symmetry, 10-26 with Octahedral symmetry, 46-80 with icosahedral symmetry.
- [U] Mathematica, 1993, follows the Kaleido series with the 5 prismatic forms moved to last, so that the nonprismatic forms become 1–75.
Nonconvex uniform polyhedra The 57 nonprismatic nonconvex forms are compiled by Wythoff constructions within Schwarz triangles.
- Main article: Nonconvex uniform polyhedron
Convex forms by Wythoff construction The convex uniform polyhedra can be named by Wythoff construction operations and can be named in relation to the regular form.
In more detail the convex uniform polyhedron are given below by their Wythoff construction within each symmetry group.
Within the Wythoff construction, there are repetitions created by lower symmetry forms. The cube is a regular polyhedron, and a square prism. The octahedron is a regular polyhedron, and a triangular antiprism. The octahedron is also a rectified tetrahedron. Many polyhedra are repeated from different construction sources and are colored differently.
The Wythoff construction applies equally to uniform polyhedra and uniform tilings on the surface of a sphere, so images of both are given. The spherical tilings including the set of hosohedrons and dihedrons which are degenerate polyhedra.
These symmetry groups are formed from the reflectional point groups in three dimensions, each represented by a fundamental triangle (p q r), where p>1, q>1, r>1 and 1/p+1/q+1/r<1.
The remaining nonreflective forms are constructed by alternation operations applied to the polyhedra with an even number of sides.
Along with the prisms and their dihedral symmetry, the spherical Wythoff construction process adds two regular classes which become degenerate as polyhedra - the dihedra and hosohedra, the first having only two faces, and the second only two vertices. The truncation of the regular hosohedra creates the prisms.
Below the convex uniform polyhedra are indexed 1-18 for the nonprismatic forms as they are presented in the tables by symmetry form. Repeated forms are in brackets.
For the infinite set of prismatic forms, they are indexed in four families:
- Hosohedrons H2... (Only as spherical tilings)
- Dihedrons D2... (Only as spherical tilings)
- Prisms P3... (Truncated hosohedrons)
- Antiprisms A3... (Snub prisms)
Summary tables
And a sampling of Dihedral symmetries:
| (p 2 2) | Parent | Truncated | Rectified | Bitruncated (tr. dual) | Birectified (dual) | Cantellated | Omnitruncated (Cantitruncated) | Snub |
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Extended Schläfli symbol | | | | | | | | |
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| t0 | t0,1 | t1 | t1,2 | t2 | t0,2 | t0,1,2 | s |
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| Wythoff symbol | 2 | p 2 | 2 2 | p | 2 | p 2 | 2 p | 2 | p | 2 2 | p 2 | 2 | p 2 2 | | | p 2 2 |
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| Coxeter-Dynkin diagram | | | | | | | | |
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| Vertex figure | p2 | (2.2p.2p) | (p.2.p.2) | (p.4.4) | 2p | (p.4.2.4) | (4.2p.4) | (3.3.p.3.2) |
|---|
Dihedral (2 2 2) |
| 2.4.4 | 2.2.2.2 | 4.4.2 |
| 2.4.2.4 | 4.4.4 | 3.3.3.2 | Dihedral (3 2 2) |
| 2.6.6 | 2.3.2.3 | 4.4.3 |
| 2.4.3.4 | 4.4.6 | 3.3.3.3 | Dihedral (4 2 2) | | 2.8.8 | 2.4.2.4 | 4.4.4 |
| 2.4.4.4 | 4.4.8 | 3.3.3.4 | Dihedral (5 2 2) | | 2.10.10 | 2.5.2.5 | 4.4.5 | | 2.4.5.4 | 4.4.10 | 3.3.3.5 | Dihedral (6 2 2) |
| 2.12.12 | 2.6.2.6 | 4.4.6 |
| 2.4.6.4 | 4.4.12 | 3.3.3.6 |
Wythoff construction operators
| Operation | Extended Schläfli symbols | Coxeter- Dynkin diagram | Description |
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| Parent | t0 | | | Any regular polyhedron or tiling |
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| Rectified | t1 | | | The edges are fully truncated into single points. The polyhedron now has the combined faces of the parent and dual. |
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Birectified Also Dual | t2 | | | The birectified (dual) is a further truncation so that the original faces are reduced to points. New faces are formed under each parent vertex. The number of edges is unchanged and are rotated 90 degrees. The dual of the regular polyhedron is also a regular polyhedron . |
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| Truncated | t0,1 | | | Each original vertex is cut off, with a new face filling the gap. Truncation has a degree of freedom, which has one solution that creates a uniform truncated polyhedron. The polyhedron has its original faces doubled in sides, and contains the faces of the dual.
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| Bitruncated | t1,2 | | | Same as truncated dual. |
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Cantellated (or rhombated) (Also expanded) | t0,2 | | | In addition to vertex truncation, each original edge is beveled with new rectangular faces appearing in their place. A uniform cantellation is half way between both the parent and dual forms.
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Omnitruncated (or cantitruncated) (or rhombitruncated) | t0,1,2 | | | The truncation and cantellation operations are applied together to create an omnitruncated form which has the parent's faces doubled in sides, the dual's faces doubled in sides, and squares where the original edges existed. |
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| Snub | s | | | The snub takes the omnitruncated form and rectifies alternate vertices. (This operation is only possible for polyhedra with all even-sided faces.) All the original faces end up with half as many sides, and the squares degenerate into edges. Since the omnitruncated forms have 3 faces/vertex, new triangles are formed. Usually these alternated faceting forms are slightly deformed thereafter in order to end again as uniform polyhedra. The possibility of the latter variation depends on the degree of freedom.
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(3 3 2) Td Tetrahedral symmetry The tetrahedral symmetry of the sphere generates 5 uniform polyhedra, and a 6th form by a snub operation.
The tetrahedral symmetry is represented by a fundamental triangle with one vertex with two mirrors, and two vertices withr three mirrors, represented by the symbol (3 3 2). It can also be represented by the Coxeter group A2 or [3,3], as well as a Coxeter-Dynkin diagram: .
There are 24 triangles, visible in the faces of the tetrakis hexahedron and alternately colored triangles on a sphere:
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(4 3 2) Oh Octahedral symmetry The octahedral symmetry of the sphere generates 7 uniform polyhedra, and a 3 more by alternation. Four of these forms are repeated from the tetrahedral symmetry table above.
The octaahedral symmetry is represented by a fundamental triangle (4 3 2) counting the mirrors at each vertex. It can also be represented by the Coxeter group B2 or [4,3], as well as a Coxeter-Dynkin diagram: .
There are 48 triangles, visible in the faces of the disdyakis dodecahedron and alternately colored triangles on a sphere:
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(5 3 2) Ih Icosahedral symmetry The icosahedral symmetry of the sphere generates 7 uniform polyhedra, and a 1 more by alternation. Only one is repeated from the tetrahedral and octahedral symmetry table above.
The icosahedral symmetry is represented by a fundamental triangle (5 3 2) counting the mirrors at each vertex. It can also be represented by the Coxeter group G2 or [5,3], as well as a Coxeter-Dynkin diagram: .
There are 60 triangles, visible in the faces of the disdyakis triacontahedron and alternately colored triangles on a sphere:
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(p 2 2) Prismatic [p,2], I2(p) family (Dph Dihedral symmetry)
- Main article: Prismatic uniform polyhedron
The dihedral symmetry of the sphere generates two infinite sets of uniform polyhedra, prisms and antiprisms, and two more infinite set of degenerate polygons, the hosohedrons and dihedrons which exists as tilings on the sphere.
The dihedral symmetry is represented by a fundamental triangle (p 2 2) counting the mirrors at each vertex. It can also be represented by the Coxeter group I2(p) or [n,2], as well as a prismatic Coxeter-Dynkin diagram: .
Below are the first five dihedral symmetries: D2 ... D6. The dihedral symmetry Dp has order 4n, represented the faces of a bipyramid, and on the sphere as an equator line on the longitude, and n equally-spaced lines of longitude.
(2 2 2) dihedral symmetry There are 8 fundamental triangles, visible in the faces of the square bipyramid (Octahedron) and alternately colored triangles on a sphere:
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| # | Name | Picture | Tiling | Coxeter-Dynkin and Schläfli symbols | Face counts by position | Element counts |
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Pos. 2
[2] (2) | Pos. 1
[ ]x[ ] (2) | Pos. 0
[ ]x[ ] (2) | Faces | Edges | Vertices |
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D2 H2 | digonal dihedron digonal hosohedron | | |
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| | | 2 | 2 | 2 |
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| D4 | truncated digonal dihedron (Same as square dihedron) | | | t= |
| | | 2 | 4 | 4 |
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P4 [7] | omnitruncated digonal dihedron (Same as cube) | | | t0,1,2 |
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| 6 | 12 | 8 |
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A2 [1] | snub digonal dihedron (Same as tetrahedron) | | | s | |
| | 4 | 6 | 4 |
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(3 2 2) D3hdihedral symmetry There are 12 fundamental triangles, visible in the faces of the hexagonal bipyramid and alternately colored triangles on a sphere:
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| # | Name | Picture | Tiling | Coxeter-Dynkin and Schläfli symbols | Face counts by position | Element counts |
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Pos. 2
[3] (2) | Pos. 1
[ ]x[ ] (3) | Pos. 0
[ ]x[ ] (3) | Faces | Edges | Vertices |
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| D3 | Trigonal dihedron | | |
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| | | 2 | 3 | 3 |
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| H3 | Trigonal hosohedron | | |
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| 3 | 3 | 2 |
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| D6 | Truncated trigonal dihedron (Same as hexagonal dihedron) | | | t |
| | | 2 | 6 | 6 |
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| P3 | Truncated trigonal hosohedron (Triangular prism) | | | t |
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| | 5 | 9 | 6 |
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| P6 | Omnitruncated trigonal dihedron (Hexagonal prism) | | | t |
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| 8 | 18 | 12 |
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A3 [2] | Snub trigonal dihedron (Same as Triangular antiprism) (Same as octahedron) | | | s |
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| | 8 | 12 | 6 |
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(4 2 2) D4hdihedral symmetry There are 16 fundamental triangles, visible in the faces of the octagonal bipyramid and alternately colored triangles on a sphere:
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| # | Name | Picture | Tiling | Coxeter-Dynkin and Schläfli symbols | Face counts by position | Element counts |
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Pos. 2
[4] (2) | Pos. 1
[ ]x[ ] (4) | Pos. 0
[ ]x[ ] (4) | Faces | Edges | Vertices |
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| D4 | square dihedron | | |
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| | | 2 | 4 | 4 |
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| H4 | square hosohedron | | |
| | |
| 4 | 4 | 2 |
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| D8 | Truncated square dihedron (Same as octagonal dihedron) | | | t |
| | | 2 | 8 | 8 |
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P4 [7] | Truncated square hosohedron (Cube) | | | t |
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| | 6 | 12 | 8 |
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| D8 | Omnitruncated square dihedron (Octagonal prism) | | | t |
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| 10 | 24 | 16 |
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| A4 | Snub square dihedron (Square antiprism) | | | t |
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| | 10 | 16 | 8 |
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(5 2 2) D5h dihedral symmetry There are 20 fundamental triangles, visible in the faces of the decagonal bipyramid and alternately colored triangles on a sphere:
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| # | Name | Picture | Tiling | Coxeter-Dynkin and Schläfli symbols | Face counts by position | Element counts |
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Pos. 2
[5] (2) | Pos. 1
[ ]x[ ] (5) | Pos. 0
[ ]x[ ] (5) | Faces | Edges | Vertices |
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| D5 | Pentagonal dihedron | | |
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| | | 2 | 5 | 5 |
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| H5 | Pentagonal hosohedron | | |
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| 5 | 5 | 2 |
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| D10 | Truncated pentagonal dihedron (Same as decagonal dihedron) | | | t |
| | | 2 | 10 | 10 |
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| P5 | Truncated pentagonal hosohedron (Same as pentagonal prism) | | | t |
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| | 7 | 15 | 10 |
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| P10 | Omnitruncated pentagonal dihedron (Decagonal prism) | | | t |
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| 12 | 30 | 20 |
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| A5 | Snub pentagonal dihedron (Pentagonal antiprism) | | | t |
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| | 12 | 20 | 10 |
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(6 2 2) D6hdihedral symmtry There are 24 fundamental triangles, visible in the faces of the dodecagonal bipyramid and alternately colored triangles on a sphere.
| # | Name | Picture | Tiling | Coxeter-Dynkin and Schläfli symbols | Face counts by position | Element counts |
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Pos. 2
[6] (2) | Pos. 1
[ ]x[ ] (6) | Pos. 0
[ ]x[ ] (6) | Faces | Edges | Vertices |
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| D6 | Hexagonal dihedron | | |
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| | | 2 | 6 | 6 |
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| H6 | Hexagonal hosohedron | | |
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| 6 | 6 | 2 |
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| D12 | Truncated hexagonal dihedron (Same as dodecagonal dihedron) | | | t |
| | | 2 | 12 | 12 |
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| H6 | Truncated hexagonal hosohedron (Same as hexagonal prism) | | | t |
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| | 8 | 18 | 12 |
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| P12 | Omnitruncated hexagonal dihedron (Dodecagonal prism) | | | t |
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| 14 | 36 | 24 |
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| A6 | Snub hexagonal dihedron (Hexagonal antiprism) | | | t |
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| | 14 | 24 | 12 |
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See also
External links
Uniform Polyhedra
- Software able to generate and print nets for all uniform polyhedra. Used to create many of the images on this page.
Paper models:
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