Example regular polytopes

Regular (2D) polygons
Convex	Star
{5}	{5/2}
Regular (3D) polyhedra
Convex	Star
{5,3}	{5/2,5}
Regular 4D polytopes
Convex	Star
{5,3,3}	{5/2,5,3}
Regular 2D tessellations
Euclidean	Hyperbolic
{4,4}	{5,4}
Regular 3D tessellations
Euclidean	Hyperbolic
{4,3,4}	{5,3,4}

This article lists the regular polytopes and regular polytope compounds in Euclidean, spherical and hyperbolic spaces.

The Schläfli symbol describes every regular tessellation of an n-sphere, Euclidean and hyperbolic spaces. A Schläfli symbol describing an n-polytope equivalently describes a tessellation of an (n − 1)-sphere. In addition, the symmetry of a regular polytope or tessellation is expressed as a Coxeter group, which Coxeter expressed identically to the Schläfli symbol, except delimiting by square brackets, a notation that is called Coxeter notation. Another related symbol is the Coxeter–Dynkin diagram which represents a symmetry group with no rings, and the represents regular polytope or tessellation with a ring on the first node. For example, the cube has Schläfli symbol {4,3}, and with its octahedral symmetry, [4,3] or , it is represented by Coxeter diagram .

The regular polytopes are grouped by dimension and subgrouped by convex, nonconvex and infinite forms. Nonconvex forms use the same vertices as the convex forms, but have intersecting facets. Infinite forms tessellate a one-lower-dimensional Euclidean space.

Infinite forms can be extended to tessellate a hyperbolic space. Hyperbolic space is like normal space at a small scale, but parallel lines diverge at a distance. This allows vertex figures to have negative angle defects, like making a vertex with seven equilateral triangles and allowing it to lie flat. It cannot be done in a regular plane, but can be at the right scale of a hyperbolic plane.

A more general definition of regular polytopes which do not have simple Schläfli symbols includes regular skew polytopes and regular skew apeirotopes with nonplanar facets or vertex figures.

Overview

This table shows a summary of regular polytope counts by dimension.

Note that the Euclidean and hyperbolic tilings are given one dimension more than what would be expected. This is because of an analogy with finite polytopes: a convex regular n-polytope can be seen as a tessellation of (n−1)-dimensional spherical space. Thus the three regular tilings of the Euclidean plane (by triangles, squares, and hexagons) are listed under dimension three rather than two.

Dim.	Finite			Euclidean	Hyperbolic			Compounds
					Compact		Paracompact
	Convex	Star	Skew	Convex	Convex	Star	Convex	Convex	Star
1	1	none	none	1	none	none	none	none	none
2	${\displaystyle \infty }$	${\displaystyle \infty }$	${\displaystyle \infty }$	1	1	none	none	${\displaystyle \infty }$	${\displaystyle \infty }$
3	5	4	?	3	${\displaystyle \infty }$	${\displaystyle \infty }$	${\displaystyle \infty }$	5	none
4	6	10	?	1	4	none	11	26	20
5	3	none	?	3	5	4	2	none	none
6	3	none	?	1	none	none	5	none	none
7	3	none	?	1	none	none	none	3	none
8	3	none	?	1	none	none	none	6	none
9+	3	none	?	1	none	none	none	[lower-alpha 1]	none

There are no Euclidean regular star tessellations in any number of dimensions.

One dimension

A Coxeter diagram represent mirror "planes" as nodes, and puts a ring around a node if a point is not on the plane. A dion { }, , is a point p and its mirror image point p', and the line segment between them.

A one-dimensional polytope or 1-polytope is a closed line segment, bounded by its two endpoints. A 1-polytope is regular by definition and is represented by Schläfli symbol { },^[1][2] or a Coxeter diagram with a single ringed node, . Norman Johnson calls it a dion^[3] and gives it the Schläfli symbol { }.

Although trivial as a polytope, it appears as the edges of polygons and other higher dimensional polytopes.^[4] It is used in the definition of uniform prisms like Schläfli symbol { }×{p}, or Coxeter diagram as a Cartesian product of a line segment and a regular polygon.^[5]

Two dimensions (polygons)

The two-dimensional polytopes are called polygons. Regular polygons are equilateral and cyclic. A p-gonal regular polygon is represented by Schläfli symbol {p}.

Usually only convex polygons are considered regular, but star polygons, like the pentagram, can also be considered regular. They use the same vertices as the convex forms, but connect in an alternate connectivity which passes around the circle more than once to be completed.

Star polygons should be called nonconvex rather than concave because the intersecting edges do not generate new vertices and all the vertices exist on a circle boundary.

Convex

The Schläfli symbol {p} represents a regular p-gon.

Name	Triangle (2-simplex)	Square (2-orthoplex) (2-cube)	Pentagon (2-pentagonal polytope)	Hexagon	Heptagon	Octagon
Schläfli	{3}	{4}	{5}	{6}	{7}	{8}
Symmetry	D3, [3]	D4, [4]	D5, [5]	D6, [6]	D7, [7]	D8, [8]
Coxeter
Image
Name	Nonagon (Enneagon)	Decagon	Hendecagon	Dodecagon	Tridecagon	Tetradecagon
Schläfli	{9}	{10}	{11}	{12}	{13}	{14}
Symmetry	D9, [9]	D10, [10]	D11, [11]	D12, [12]	D13, [13]	D14, [14]
Dynkin
Image
Name	Pentadecagon	Hexadecagon	Heptadecagon	Octadecagon	Enneadecagon	Icosagon	...p-gon
Schläfli	{15}	{16}	{17}	{18}	{19}	{20}	{p}
Symmetry	D15, [15]	D16, [16]	D17, [17]	D18, [18]	D19, [19]	D20, [20]	Dp, [p]
Dynkin
Image

Spherical

The regular digon {2} can be considered to be a degenerate regular polygon. It can be realized non-degenerately in some non-Euclidean spaces, such as on the surface of a sphere or torus. For example, digon can be realised non-degenerately as a spherical lune. A monogon {1} could also be realised on the sphere as a single point with a great circle through it.^[6] However, a monogon is not a valid abstract polytope because its single edge is incident to only one vertex rather than two.

Name	Monogon	Digon
Schläfli symbol	{1}	{2}
Symmetry	D1, [ ]	D2, [2]
Coxeter diagram	or
Image

Stars

There exist infinitely many regular star polytopes in two dimensions, whose Schläfli symbols consist of rational numbers {n/m}. They are called star polygons and share the same vertex arrangements of the convex regular polygons.

In general, for any natural number n, there are n-pointed star regular polygonal stars with Schläfli symbols {n/m} for all m such that m < n/2 (strictly speaking {n/m}={n/(n−m)}) and m and n are coprime (as such, all stellations of a polygon with a prime number of sides will be regular stars). Cases where m and n are not coprime are called compound polygons.

Name	Pentagram	Heptagrams		Octagram	Enneagrams		Decagram	...n-grams
Schläfli	{5/2}	{7/2}	{7/3}	{8/3}	{9/2}	{9/4}	{10/3}	{p/q}
Symmetry	D5, [5]	D7, [7]		D8, [8]	D9, [9],		D10, [10]	Dp, [p]
Coxeter
Image

Regular star polygons up to 20 sides

{11/2}	{11/3}	{11/4}	{11/5}	{12/5}	{13/2}	{13/3}	{13/4}	{13/5}	{13/6}
{14/3}	{14/5}	{15/2}	{15/4}	{15/7}	{16/3}	{16/5}	{16/7}
{17/2}	{17/3}	{17/4}	{17/5}	{17/6}	{17/7}	{17/8}	{18/5}	{18/7}
{19/2}	{19/3}	{19/4}	{19/5}	{19/6}	{19/7}	{19/8}	{19/9}	{20/3}	{20/7}	{20/9}

Star polygons that can only exist as spherical tilings, similarly to the monogon and digon, may exist (for example: {3/2}, {5/3}, {5/4}, {7/4}, {9/5}), however these do not appear to have been studied in detail.

There also exist failed star polygons, such as the piangle, which do not cover the surface of a circle finitely many times.^[7]

Skew polygons

In 3-dimensional space, a regular skew polygon is called an antiprismatic polygon, with the vertex arrangement of an antiprism, and a subset of edges, zig-zagging between top and bottom polygons.

Example regular skew zig-zag polygons

Hexagon	Octagon	Decagons
D3d, [2+,6]	D4d, [2+,8]	D5d, [2+,10]
{3}#{ }	{4}#{ }	{5}#{ }	{5/2}#{ }	{5/3}#{ }

In 4-dimensions a regular skew polygon can have vertices on a Clifford torus and related by a Clifford displacement. Unlike antiprismatic skew polygons, skew polygons on double rotations can include an odd-number of sides.

They can be seen in the Petrie polygons of the convex regular 4-polytopes, seen as regular plane polygons in the perimeter of Coxeter plane projection:

Pentagon	Octagon	Dodecagon	Triacontagon
5-cell	16-cell	24-cell	600-cell

Three dimensions (polyhedra)

In three dimensions, polytopes are called polyhedra:

A regular polyhedron with Schläfli symbol {p,q}, Coxeter diagrams , has a regular face type {p}, and regular vertex figure {q}.

A vertex figure (of a polyhedron) is a polygon, seen by connecting those vertices which are one edge away from a given vertex. For regular polyhedra, this vertex figure is always a regular (and planar) polygon.

Existence of a regular polyhedron {p,q} is constrained by an inequality, related to the vertex figure's angle defect:

${\displaystyle {\begin{aligned}&{\frac {1}{p}}+{\frac {1}{q}}>{\frac {1}{2}}:{\text{Polyhedron (existing in Euclidean 3-space)}}\\[6pt]&{\frac {1}{p}}+{\frac {1}{q}}={\frac {1}{2}}:{\text{Euclidean plane tiling}}\\[6pt]&{\frac {1}{p}}+{\frac {1}{q}}<{\frac {1}{2}}:{\text{Hyperbolic plane tiling}}\end{aligned}}}$

By enumerating the permutations, we find five convex forms, four star forms and three plane tilings, all with polygons {p} and {q} limited to: {3}, {4}, {5}, {5/2}, and {6}.

Beyond Euclidean space, there is an infinite set of regular hyperbolic tilings.

Convex

The five convex regular polyhedra are called the Platonic solids. The vertex figure is given with each vertex count. All these polyhedra have an Euler characteristic (χ) of 2.

Name	Schläfli {p,q}	Coxeter	Image (solid)	Image (sphere)	Faces {p}	Edges	Vertices {q}	Symmetry	Dual
Tetrahedron (3-simplex)	{3,3}				4 {3}	6	4 {3}	Td [3,3] (*332)	(self)
Hexahedron Cube (3-cube)	{4,3}				6 {4}	12	8 {3}	Oh [4,3] (*432)	Octahedron
Octahedron (3-orthoplex)	{3,4}				8 {3}	12	6 {4}	Oh [4,3] (*432)	Cube
Dodecahedron	{5,3}				12 {5}	30	20 {3}	Ih [5,3] (*532)	Icosahedron
Icosahedron	{3,5}				20 {3}	30	12 {5}	Ih [5,3] (*532)	Dodecahedron

Spherical

In spherical geometry, regular spherical polyhedra (tilings of the sphere) exist that would otherwise be degenerate as polytopes. These are the hosohedra {2,n} and their dual dihedra {n,2}. Coxeter calls these cases "improper" tessellations.^[8]

The first few cases (n from 2 to 6) are listed below.

Hosohedra

Name	Schläfli {2,p}	Coxeter diagram	Image (sphere)	Faces {2}π/p	Edges	Vertices {p}	Symmetry	Dual
Digonal hosohedron	{2,2}			2 {2}π/2	2	2 {2}π/2	D2h [2,2] (*222)	Self
Trigonal hosohedron	{2,3}			3 {2}π/3	3	2 {3}	D3h [2,3] (*322)	Trigonal dihedron
Square hosohedron	{2,4}			4 {2}π/4	4	2 {4}	D4h [2,4] (*422)	Square dihedron
Pentagonal hosohedron	{2,5}			5 {2}π/5	5	2 {5}	D5h [2,5] (*522)	Pentagonal dihedron
Hexagonal hosohedron	{2,6}			6 {2}π/6	6	2 {6}	D6h [2,6] (*622)	Hexagonal dihedron

Dihedra

Name	Schläfli {p,2}	Coxeter diagram	Image (sphere)	Faces {p}	Edges	Vertices {2}	Symmetry	Dual
Digonal dihedron	{2,2}			2 {2}π/2	2	2 {2}π/2	D2h [2,2] (*222)	Self
Trigonal dihedron	{3,2}			2 {3}	3	3 {2}π/3	D3h [3,2] (*322)	Trigonal hosohedron
Square dihedron	{4,2}			2 {4}	4	4 {2}π/4	D4h [4,2] (*422)	Square hosohedron
Pentagonal dihedron	{5,2}			2 {5}	5	5 {2}π/5	D5h [5,2] (*522)	Pentagonal hosohedron
Hexagonal dihedron	{6,2}			2 {6}	6	6 {2}π/6	D6h [6,2] (*622)	Hexagonal hosohedron

Star-dihedra and hosohedra {p/q,2} and {2,p/q} also exist for any star polygon {p/q}.

Stars

The regular star polyhedra are called the Kepler–Poinsot polyhedra and there are four of them, based on the vertex arrangements of the dodecahedron {5,3} and icosahedron {3,5}:

As spherical tilings, these star forms overlap the sphere multiple times, called its density, being 3 or 7 for these forms. The tiling images show a single spherical polygon face in yellow.

Name	Image (skeletonic)	Image (solid)	Image (sphere)	Stellation diagram	Schläfli {p,q} and Coxeter	Faces {p}	Edges	Vertices {q} verf.	χ	Density	Symmetry	Dual
Small stellated dodecahedron					{5/2,5}	12 {5/2}	30	12 {5}	−6	3	Ih [5,3] (*532)	Great dodecahedron
Great dodecahedron					{5,5/2}	12 {5}	30	12 {5/2}	−6	3	Ih [5,3] (*532)	Small stellated dodecahedron
Great stellated dodecahedron					{5/2,3}	12 {5/2}	30	20 {3}	2	7	Ih [5,3] (*532)	Great icosahedron
Great icosahedron					{3,5/2}	20 {3}	30	12 {5/2}	2	7	Ih [5,3] (*532)	Great stellated dodecahedron

There are infinitely many failed star polyhedra. These are also spherical tilings with star polygons in their Schläfli symbols, but they do not cover a sphere finitely many times. Some examples are {5/2,4}, {5/2,9}, {7/2,3}, {5/2,5/2}, {7/2,7/3}, {4,5/2}, and {3,7/3}.

Skew polyhedra

Regular skew polyhedra are generalizations to the set of regular polyhedron which include the possibility of nonplanar vertex figures.

For 4-dimensional skew polyhedra, Coxeter offered a modified Schläfli symbol {l,m|n} for these figures, with {l,m} implying the vertex figure, m l-gons around a vertex, and n-gonal holes. Their vertex figures are skew polygons, zig-zagging between two planes.

The regular skew polyhedra, represented by {l,m|n}, follow this equation:

2 sin(π/l) sin(π/m) = cos(π/n)

Four of them can be seen in 4-dimensions as a subset of faces of four regular 4-polytopes, sharing the same vertex arrangement and edge arrangement:

{4, 6 | 3}	{6, 4 | 3}	{4, 8 | 3}	{8, 4 | 3}

Four dimensions

Regular 4-polytopes with Schläfli symbol ${\displaystyle \{p,q,r\}}$ have cells of type ${\displaystyle \{p,q\}}$, faces of type ${\displaystyle \{p\}}$, edge figures ${\displaystyle \{r\}}$, and vertex figures ${\displaystyle \{q,r\}}$.

• A vertex figure (of a 4-polytope) is a polyhedron, seen by the arrangement of neighboring vertices around a given vertex. For regular 4-polytopes, this vertex figure is a regular polyhedron.
• An edge figure is a polygon, seen by the arrangement of faces around an edge. For regular 4-polytopes, this edge figure will always be a regular polygon.

The existence of a regular 4-polytope ${\displaystyle \{p,q,r\}}$ is constrained by the existence of the regular polyhedra ${\displaystyle \{p,q\},\{q,r\}}$. A suggested name for 4-polytopes is "polychoron".^[9]

Each will exist in a space dependent upon this expression:

${\displaystyle \sin \left({\frac {\pi }{p}}\right)\sin \left({\frac {\pi }{r}}\right)-\cos \left({\frac {\pi }{q}}\right)}$

${\displaystyle >0}$ : Hyperspherical 3-space honeycomb or 4-polytope

${\displaystyle =0}$ : Euclidean 3-space honeycomb

${\displaystyle <0}$ : Hyperbolic 3-space honeycomb

These constraints allow for 21 forms: 6 are convex, 10 are nonconvex, one is a Euclidean 3-space honeycomb, and 4 are hyperbolic honeycombs.

The Euler characteristic ${\displaystyle \chi }$ for convex 4-polytopes is zero: ${\displaystyle \chi =V+F-E-C=0}$

Convex

The 6 convex regular 4-polytopes are shown in the table below. All these 4-polytopes have an Euler characteristic (χ) of 0.

Name	Schläfli {p,q,r}	Coxeter	Cells {p,q}	Faces {p}	Edges {r}	Vertices {q,r}	Dual {r,q,p}
5-cell (4-simplex)	{3,3,3}		5 {3,3}	10 {3}	10 {3}	5 {3,3}	(self)
8-cell (4-cube) (Tesseract)	{4,3,3}		8 {4,3}	24 {4}	32 {3}	16 {3,3}	16-cell
16-cell (4-orthoplex)	{3,3,4}		16 {3,3}	32 {3}	24 {4}	8 {3,4}	Tesseract
24-cell	{3,4,3}		24 {3,4}	96 {3}	96 {3}	24 {4,3}	(self)
120-cell	{5,3,3}		120 {5,3}	720 {5}	1200 {3}	600 {3,3}	600-cell
600-cell	{3,3,5}		600 {3,3}	1200 {3}	720 {5}	120 {3,5}	120-cell

5-cell	8-cell	16-cell	24-cell	120-cell	600-cell
{3,3,3}	{4,3,3}	{3,3,4}	{3,4,3}	{5,3,3}	{3,3,5}
Wireframe (Petrie polygon) skew orthographic projections
Solid orthographic projections
tetrahedral envelope (cell/ vertex-centered)	cubic envelope (cell-centered)	cubic envelope (cell-centered)	cuboctahedral envelope (cell-centered)	truncated rhombic triacontahedron envelope (cell-centered)	Pentakis icosidodecahedral envelope (vertex-centered)
Wireframe Schlegel diagrams (Perspective projection)
(cell-centered)	(cell-centered)	(cell-centered)	(cell-centered)	(cell-centered)	(vertex-centered)
Wireframe stereographic projections (Hyperspherical)

Spherical

Di-4-topes and hoso-4-topes exist as regular tessellations of the 3-sphere.

Regular di-4-topes (2 facets) include: {3,3,2}, {3,4,2}, {4,3,2}, {5,3,2}, {3,5,2}, {p,2,2}, and their hoso-4-tope duals (2 vertices): {2,3,3}, {2,4,3}, {2,3,4}, {2,3,5}, {2,5,3}, {2,2,p}. 4-polytopes of the form {2,p,2} are the same as {2,2,p}. There are also the cases {p,2,q} which have dihedral cells and hosohedral vertex figures.

Regular hoso-4-topes as 3-sphere honeycombs

Schläfli {2,p,q}	Coxeter	Cells {2,p}π/q	Faces {2}π/p,π/q	Edges	Vertices	Vertex figure {p,q}	Symmetry	Dual
{2,3,3}		4 {2,3}π/3	6 {2}π/3,π/3	4	2	{3,3}	[2,3,3]	{3,3,2}
{2,4,3}		6 {2,4}π/3	12 {2}π/4,π/3	8	2	{4,3}	[2,4,3]	{3,4,2}
{2,3,4}		8 {2,3}π/4	12 {2}π/3,π/4	6	2	{3,4}	[2,4,3]	{4,3,2}
{2,5,3}		12 {2,5}π/3	30 {2}π/5,π/3	20	2	{5,3}	[2,5,3]	{3,5,2}
{2,3,5}		20 {2,3}π/5	30 {2}π/3,π/5	12	2	{3,5}	[2,5,3]	{5,3,2}

Stars

There are ten regular star 4-polytopes, which are called the Schläfli–Hess 4-polytopes. Their vertices are based on the convex 120-cell {5,3,3} and 600-cell {3,3,5}.

Ludwig Schläfli found four of them and skipped the last six because he would not allow forms that failed the Euler characteristic on cells or vertex figures (for zero-hole tori: F+V−E=2). Edmund Hess (1843–1903) completed the full list of ten in his German book Einleitung in die Lehre von der Kugelteilung mit besonderer Berücksichtigung ihrer Anwendung auf die Theorie der Gleichflächigen und der gleicheckigen Polyeder (1883).

There are 4 unique edge arrangements and 7 unique face arrangements from these 10 regular star 4-polytopes, shown as orthogonal projections:

Name	Wireframe	Solid	Schläfli {p, q, r} Coxeter	Cells {p, q}	Faces {p}	Edges {r}	Vertices {q, r}	Density	χ	Symmetry group	Dual {r, q,p}
Icosahedral 120-cell (faceted 600-cell)			{3,5,5/2}	120 {3,5}	1200 {3}	720 {5/2}	120 {5,5/2}	4	480	H4 [5,3,3]	Small stellated 120-cell
Small stellated 120-cell			{5/2,5,3}	120 {5/2,5}	720 {5/2}	1200 {3}	120 {5,3}	4	−480	H4 [5,3,3]	Icosahedral 120-cell
Great 120-cell			{5,5/2,5}	120 {5,5/2}	720 {5}	720 {5}	120 {5/2,5}	6	0	H4 [5,3,3]	Self-dual
Grand 120-cell			{5,3,5/2}	120 {5,3}	720 {5}	720 {5/2}	120 {3,5/2}	20	0	H4 [5,3,3]	Great stellated 120-cell
Great stellated 120-cell			{5/2,3,5}	120 {5/2,3}	720 {5/2}	720 {5}	120 {3,5}	20	0	H4 [5,3,3]	Grand 120-cell
Grand stellated 120-cell			{5/2,5,5/2}	120 {5/2,5}	720 {5/2}	720 {5/2}	120 {5,5/2}	66	0	H4 [5,3,3]	Self-dual
Great grand 120-cell			{5,5/2,3}	120 {5,5/2}	720 {5}	1200 {3}	120 {5/2,3}	76	−480	H4 [5,3,3]	Great icosahedral 120-cell
Great icosahedral 120-cell (great faceted 600-cell)			{3,5/2,5}	120 {3,5/2}	1200 {3}	720 {5}	120 {5/2,5}	76	480	H4 [5,3,3]	Great grand 120-cell
Grand 600-cell			{3,3,5/2}	600 {3,3}	1200 {3}	720 {5/2}	120 {3,5/2}	191	0	H4 [5,3,3]	Great grand stellated 120-cell
Great grand stellated 120-cell			{5/2,3,3}	120 {5/2,3}	720 {5/2}	1200 {3}	600 {3,3}	191	0	H4 [5,3,3]	Grand 600-cell

There are 4 failed potential regular star 4-polytopes permutations: {3,5/2,3}, {4,3,5/2}, {5/2,3,4}, {5/2,3,5/2}. Their cells and vertex figures exist, but they do not cover a hypersphere with a finite number of repetitions.

Five and more dimensions

In five dimensions, a regular polytope can be named as ${\displaystyle \{p,q,r,s\}}$ where ${\displaystyle \{p,q,r\}}$ is the 4-face type, ${\displaystyle \{p,q\}}$ is the cell type, ${\displaystyle \{p\}}$ is the face type, and ${\displaystyle \{s\}}$ is the face figure, ${\displaystyle \{r,s\}}$ is the edge figure, and ${\displaystyle \{q,r,s\}}$ is the vertex figure.

A vertex figure (of a 5-polytope) is a 4-polytope, seen by the arrangement of neighboring vertices to each vertex.

An edge figure (of a 5-polytope) is a polyhedron, seen by the arrangement of faces around each edge.

A face figure (of a 5-polytope) is a polygon, seen by the arrangement of cells around each face.

A regular 5-polytope ${\displaystyle \{p,q,r,s\}}$ exists only if ${\displaystyle \{p,q,r\}}$ and ${\displaystyle \{q,r,s\}}$ are regular 4-polytopes.

The space it fits in is based on the expression:

${\displaystyle {\frac {\cos ^{2}\left({\frac {\pi }{q}}\right)}{\sin ^{2}\left({\frac {\pi }{p}}\right)}}+{\frac {\cos ^{2}\left({\frac {\pi }{r}}\right)}{\sin ^{2}\left({\frac {\pi }{s}}\right)}}}$

${\displaystyle <1}$ : Spherical 4-space tessellation or 5-space polytope

${\displaystyle =1}$ : Euclidean 4-space tessellation

${\displaystyle >1}$ : hyperbolic 4-space tessellation

Enumeration of these constraints produce 3 convex polytopes, zero nonconvex polytopes, 3 4-space tessellations, and 5 hyperbolic 4-space tessellations. There are no non-convex regular polytopes in five dimensions or higher.

Convex

In dimensions 5 and higher, there are only three kinds of convex regular polytopes.^[10]

Name	Schläfli Symbol {p1,...,pn−1}	Coxeter	k-faces	Facet type	Vertex figure	Dual
n-simplex	{3n−1}	...	${\displaystyle {{n+1} \choose {k+1}}}$	{3n−2}	{3n−2}	Self-dual
n-cube	{4,3n−2}	...	${\displaystyle 2^{n-k}{n \choose k}}$	{4,3n−3}	{3n−2}	n-orthoplex
n-orthoplex	{3n−2,4}	...	${\displaystyle 2^{k+1}{n \choose {k+1}}}$	{3n−2}	{3n−3,4}	n-cube

There are also improper cases where some numbers in the Schläfli symbol are 2. For example, {p,q,r,...2} is an improper regular spherical polytope whenever {p,q,r...} is a regular spherical polytope, and {2,...p,q,r} is an improper regular spherical polytope whenever {...p,q,r} is a regular spherical polytope. Such polytopes may also be used as facets, yielding forms such as {p,q,...2...y,z}.

5 dimensions

Name	Schläfli Symbol {p,q,r,s} Coxeter	Facets {p,q,r}	Cells {p,q}	Faces {p}	Edges	Vertices	Face figure {s}	Edge figure {r,s}	Vertex figure {q,r,s}
5-simplex	{3,3,3,3}	6 {3,3,3}	15 {3,3}	20 {3}	15	6	{3}	{3,3}	{3,3,3}
5-cube	{4,3,3,3}	10 {4,3,3}	40 {4,3}	80 {4}	80	32	{3}	{3,3}	{3,3,3}
5-orthoplex	{3,3,3,4}	32 {3,3,3}	80 {3,3}	80 {3}	40	10	{4}	{3,4}	{3,3,4}

5-simplex

5-cube

5-orthoplex

6 dimensions

Name	Schläfli	Vertices	Edges	Faces	Cells	4-faces	5-faces	χ
6-simplex	{3,3,3,3,3}	7	21	35	35	21	7	0
6-cube	{4,3,3,3,3}	64	192	240	160	60	12	0
6-orthoplex	{3,3,3,3,4}	12	60	160	240	192	64	0

6-simplex

6-cube

6-orthoplex

7 dimensions

Name	Schläfli	Vertices	Edges	Faces	Cells	4-faces	5-faces	6-faces	χ
7-simplex	{3,3,3,3,3,3}	8	28	56	70	56	28	8	2
7-cube	{4,3,3,3,3,3}	128	448	672	560	280	84	14	2
7-orthoplex	{3,3,3,3,3,4}	14	84	280	560	672	448	128	2

7-simplex

7-cube

7-orthoplex

8 dimensions

Name	Schläfli	Vertices	Edges	Faces	Cells	4-faces	5-faces	6-faces	7-faces	χ
8-simplex	{3,3,3,3,3,3,3}	9	36	84	126	126	84	36	9	0
8-cube	{4,3,3,3,3,3,3}	256	1024	1792	1792	1120	448	112	16	0
8-orthoplex	{3,3,3,3,3,3,4}	16	112	448	1120	1792	1792	1024	256	0

8-simplex

8-cube

8-orthoplex

9 dimensions

Name	Schläfli	Vertices	Edges	Faces	Cells	4-faces	5-faces	6-faces	7-faces	8-faces	χ
9-simplex	{38}	10	45	120	210	252	210	120	45	10	2
9-cube	{4,37}	512	2304	4608	5376	4032	2016	672	144	18	2
9-orthoplex	{37,4}	18	144	672	2016	4032	5376	4608	2304	512	2

9-simplex

9-cube

9-orthoplex

10 dimensions

Name	Schläfli	Vertices	Edges	Faces	Cells	4-faces	5-faces	6-faces	7-faces	8-faces	9-faces	χ
10-simplex	{39}	11	55	165	330	462	462	330	165	55	11	0
10-cube	{4,38}	1024	5120	11520	15360	13440	8064	3360	960	180	20	0
10-orthoplex	{38,4}	20	180	960	3360	8064	13440	15360	11520	5120	1024	0

10-simplex

10-cube

10-orthoplex

...

Regular projective polytopes

A projective regular (n+1)-polytope exists when an original regular n-spherical tessellation, {p,q,...}, is centrally symmetric. Such a polytope is named hemi-{p,q,...}, and contain half as many elements. Coxeter gives a symbol {p,q,...}/2, while McMullen writes {p,q,...}_h/2 with h as the coxeter number.^[11]

Even-sided regular polygons have hemi-2n-gon projective polygons, {2p}/2.

There are 4 regular projective polyhedra related to 4 of 5 Platonic solids.

The hemi-cube and hemi-octahedron generalize as hemi-n-cubes and hemi-n-orthoplexes in any dimensions.

Regular projective polyhedra

3-dimensional regular hemi-polytopes

Name	Coxeter McMullen	Image	Faces	Edges	Vertices	χ
Hemi-cube	{4,3}/2 {4,3}3		3	6	4	1
Hemi-octahedron	{3,4}/2 {3,4}3		4	6	3	1
Hemi-dodecahedron	{5,3}/2 {5,3}5		6	15	10	1
Hemi-icosahedron	{3,5}/2 {3,5}5		10	15	6	1

Apeirotopes

An apeirotope or infinite polytope is a polytope which has infinitely many facets. An n-apeirotope is an infinite n-polytope: a 2-apeirotope or apeirogon is an infinite polygon, a 3-apeirotope or apeirohedron is an infinite polyhedron, etc.

There are two main geometric classes of apeirotope:^[12]

• Regular honeycombs in n dimensions, which completely fill an n-dimensional space.
• Regular skew apeirotopes, comprising an n-dimensional manifold in a higher space.

One dimension (apeirogons)

The straight apeirogon is a regular tessellation of the line, subdividing it into infinitely many equal segments. It has infinitely many vertices and edges. Its Schläfli symbol is {∞}, and Coxeter diagram .

......

It exists as the limit of the p-gon as p tends to infinity, as follows:

Name	Monogon	Digon	Triangle	Square	Pentagon	Hexagon	Heptagon	p-gon	Apeirogon
Schläfli	{1}	{2}	{3}	{4}	{5}	{6}	{7}	{p}	{∞}
Symmetry	D1, [ ]	D2, [2]	D3, [3]	D4, [4]	D5, [5]	D6, [6]	D7, [7]	[p]
Coxeter	or
Image

Apeirogons in the hyperbolic plane, most notably the regular apeirogon, {∞}, can have a curvature just like finite polygons of the Euclidean plane, with the vertices circumscribed by horocycles or hypercycles rather than circles.

Regular apeirogons that are scaled to converge at infinity have the symbol {∞} and exist on horocycles, while more generally they can exist on hypercycles.

{∞}	{πi/λ}
Apeirogon on horocycle	Apeirogon on hypercycle

Above are two regular hyperbolic apeirogons in the Poincaré disk model, the right one shows perpendicular reflection lines of divergent fundamental domains, separated by length λ.

Skew apeirogons

A skew apeirogon in two dimensions forms a zig-zag line in the plane. If the zig-zag is even and symmetrical, then the apeirogon is regular.

Skew apeirogons can be constructed in any number of dimensions. In three dimensions, a regular skew apeirogon traces out a helical spiral and may be either left- or right-handed.

2-dimensions	3-dimensions
Zig-zag apeirogon	Helix apeirogon

Two dimensions (apeirohedra)

Euclidean tilings

There are three regular tessellations of the plane. All three have an Euler characteristic (χ) of 0.

Name	Square tiling (quadrille)	Triangular tiling (deltille)	Hexagonal tiling (hextille)
Symmetry	p4m, [4,4], (*442)	p6m, [6,3], (*632)
Schläfli {p,q}	{4,4}	{3,6}	{6,3}
Coxeter diagram
Image

There are two improper regular tilings: {∞,2}, an apeirogonal dihedron, made from two apeirogons, each filling half the plane; and secondly, its dual, {2,∞}, an apeirogonal hosohedron, seen as an infinite set of parallel lines.

{∞,2},

{2,∞},

Euclidean star-tilings

There are no regular plane tilings of star polygons. There are many enumerations that fit in the plane (1/p + 1/q = 1/2), like {8/3,8}, {10/3,5}, {5/2,10}, {12/5,12}, etc., but none repeat periodically.

Hyperbolic tilings

Tessellations of hyperbolic 2-space are hyperbolic tilings. There are infinitely many regular tilings in H². As stated above, every positive integer pair {p,q} such that 1/p + 1/q < 1/2 gives a hyperbolic tiling. In fact, for the general Schwarz triangle (p, q, r) the same holds true for 1/p + 1/q + 1/r < 1.

There are a number of different ways to display the hyperbolic plane, including the Poincaré disc model which maps the plane into a circle, as shown below. It should be recognized that all of the polygon faces in the tilings below are equal-sized and only appear to get smaller near the edges due to the projection applied, very similar to the effect of a camera fisheye lens.

There are infinitely many flat regular 3-apeirotopes (apeirohedra) as regular tilings of the hyperbolic plane, of the form {p,q}, with p+q<pq/2. (previously listed above as tessellations)

• {3,7}, {3,8}, {3,9} ... {3,∞}
• {4,5}, {4,6}, {4,7} ... {4,∞}
• {5,4}, {5,5}, {5,6} ... {5,∞}
• {6,4}, {6,5}, {6,6} ... {6,∞}
• {7,3}, {7,4}, {7,5} ... {7,∞}
• {8,3}, {8,4}, {8,5} ... {8,∞}
• {9,3}, {9,4}, {9,5} ... {9,∞}
• ...
• {∞,3}, {∞,4}, {∞,5} ... {∞,∞}

A sampling:

Regular hyperbolic tiling table
Spherical (improper/Platonic)/Euclidean/hyperbolic (Poincaré disc: compact/paracompact/noncompact) tessellations with their Schläfli symbol
p \ q	2	3	4	5	6	7	8	...	∞	...	iπ/λ
2	{2,2}	{2,3}	{2,4}	{2,5}	{2,6}	{2,7}	{2,8}		{2,∞}		{2,iπ/λ}
3	{3,2}	(tetrahedron) {3,3}	(octahedron) {3,4}	(icosahedron) {3,5}	(deltille) {3,6}	{3,7}	{3,8}		{3,∞}		{3,iπ/λ}
4	{4,2}	(cube) {4,3}	(quadrille) {4,4}	{4,5}	{4,6}	{4,7}	{4,8}		{4,∞}		{4,iπ/λ}
5	{5,2}	(dodecahedron) {5,3}	{5,4}	{5,5}	{5,6}	{5,7}	{5,8}		{5,∞}		{5,iπ/λ}
6	{6,2}	(hextille) {6,3}	{6,4}	{6,5}	{6,6}	{6,7}	{6,8}		{6,∞}		{6,iπ/λ}
7	{7,2}	{7,3}	{7,4}	{7,5}	{7,6}	{7,7}	{7,8}		{7,∞}		{7,iπ/λ}
8	{8,2}	{8,3}	{8,4}	{8,5}	{8,6}	{8,7}	{8,8}		{8,∞}		{8,iπ/λ}
...
∞	{∞,2}	{∞,3}	{∞,4}	{∞,5}	{∞,6}	{∞,7}	{∞,8}	{∞,∞}	{∞,iπ/λ}
...
iπ/λ	{iπ/λ,2}	{iπ/λ,3}	{iπ/λ,4}	{iπ/λ,5}	{iπ/λ,6}	{iπ/λ,7}	{iπ/λ,8}	{iπ/λ,∞}	{iπ/λ, iπ/λ}

The tilings {p, ∞} have ideal vertices, on the edge of the Poincaré disc model. Their duals {∞, p} have ideal apeirogonal faces, meaning that they are inscribed in horocycles. One could go further (as is done in the table above) and find tilings with ultra-ideal vertices, outside the Poincaré disc, which are dual to tiles inscribed in hypercycles; in what is symbolised {p, iπ/λ} above, infinitely many tiles still fit around each ultra-ideal vertex.^[13] (Parallel lines in extended hyperbolic space meet at an ideal point; ultraparallel lines meet at an ultra-ideal point.)^[14]

Hyperbolic star-tilings

There are 2 infinite forms of hyperbolic tilings whose faces or vertex figures are star polygons: {m/2, m} and their duals {m, m/2} with m = 7, 9, 11, .... The {m/2, m} tilings are stellations of the {m, 3} tilings while the {m, m/2} dual tilings are facetings of the {3, m} tilings and greatenings of the {m, 3} tilings.

The patterns {m/2, m} and {m, m/2} continue for odd m < 7 as polyhedra: when m = 5, we obtain the small stellated dodecahedron and great dodecahedron, and when m = 3, the case degenerates to a tetrahedron. The other two Kepler–Poinsot polyhedra (the great stellated dodecahedron and great icosahedron) do not have regular hyperbolic tiling analogues. If m is even, depending on how we choose to define {m/2}, we can either obtain degenerate double covers of other tilings or compound tilings.

Name	Schläfli	Coxeter diagram	Image	Face type {p}	Vertex figure {q}	Density	Symmetry	Dual
Order-7 heptagrammic tiling	{7/2,7}			{7/2}	{7}	3	*732 [7,3]	Heptagrammic-order heptagonal tiling
Heptagrammic-order heptagonal tiling	{7,7/2}			{7}	{7/2}	3	*732 [7,3]	Order-7 heptagrammic tiling
Order-9 enneagrammic tiling	{9/2,9}			{9/2}	{9}	3	*932 [9,3]	Enneagrammic-order enneagonal tiling
Enneagrammic-order enneagonal tiling	{9,9/2}			{9}	{9/2}	3	*932 [9,3]	Order-9 enneagrammic tiling
Order-11 hendecagrammic tiling	{11/2,11}			{11/2}	{11}	3	*11.3.2 [11,3]	Hendecagrammic-order hendecagonal tiling
Hendecagrammic-order hendecagonal tiling	{11,11/2}			{11}	{11/2}	3	*11.3.2 [11,3]	Order-11 hendecagrammic tiling
Order-p p-grammic tiling	{p/2,p}			{p/2}	{p}	3	*p32 [p,3]	p-grammic-order p-gonal tiling
p-grammic-order p-gonal tiling	{p,p/2}			{p}	{p/2}	3	*p32 [p,3]	Order-p p-grammic tiling

Skew apeirohedra in Euclidean 3-space

There are three regular skew apeirohedra in Euclidean 3-space, with regular skew polygon vertex figures.^[15][16][17] They share the same vertex arrangement and edge arrangement of 3 convex uniform honeycombs.

• 6 squares around each vertex: {4,6|4}
• 4 hexagons around each vertex: {6,4|4}
• 6 hexagons around each vertex: {6,6|3}

12 "pure" apeirohedra in Euclidean 3-space based on the structure of the cubic honeycomb, {4,3,4}.^[18] A π petrie dual operator replaces faces with petrie polygons; δ is a dual operator reverses vertices and faces; φ_k is a kth facetting operator; η is a halving operator, and σ skewing halving operator.

Regular skew polyhedra
{4,6|4}	{6,4|4}	{6,6|3}

There are thirty regular apeirohedra in Euclidean 3-space.^[19] These include those listed above, as well as 8 other "pure" apeirohedra, all related to the cubic honeycomb, {4,3,4}, with others having skew polygon faces: {6,6}₄, {4,6}₄, {6,4}₆, {∞,3}^a, {∞,3}^b, {∞,4}^.*3, {∞,4}_6,4, {∞,6}_4,4, and {∞,6}_6,3.

Skew apeirohedra in hyperbolic 3-space

There are 31 regular skew apeirohedra in hyperbolic 3-space:^[20]

• 14 are compact: {8,10|3}, {10,8|3}, {10,4|3}, {4,10|3}, {6,4|5}, {4,6|5}, {10,6|3}, {6,10|3}, {8,8|3}, {6,6|4}, {10,10|3},{6,6|5}, {8,6|3}, and {6,8|3}.
• 17 are paracompact: {12,10|3}, {10,12|3}, {12,4|3}, {4,12|3}, {6,4|6}, {4,6|6}, {8,4|4}, {4,8|4}, {12,6|3}, {6,12|3}, {12,12|3}, {6,6|6}, {8,6|4}, {6,8|4}, {12,8|3}, {8,12|3}, and {8,8|4}.