# Hypercube

n -hypercube
Rankn
TypeRegular
Notation
Coxeter diagramx4o3o3...3o (...)
Schläfli symbol{4,3,3,...,3}
Elements
Facets2n  n-1 -hypercubes
Vertices${\displaystyle 2^{n}}$
Vertex figure(n  − 1)-simplex, edge length 2
Measures (edge length 1)
Circumradius${\displaystyle {\frac {\sqrt {n}}{2}}}$
Inradius${\displaystyle {\frac {1}{2}}=0.5}$
Volume1
Height1
Central density1
Number of external pieces${\displaystyle 2n}$
Level of complexity1
Related polytopes
Dualn -orthoplex
ConjugateNone
Abstract & topological properties
Flag count${\displaystyle n!\times 2^{n}}$
Euler characteristic0 if n  even
2 if n  odd
OrientableYes
Properties
SymmetryBn , order ${\displaystyle n!\times 2^{n}}$
ConvexYes
NatureTame

A hypercube is the simplest center-symmetric polytope in each respective dimension, by facet count. Hypercubes are a direct generalization of squares and cubes to higher dimensions. The n -dimensional hypercube, or simply the n -cube, has 2n  vertices, such that for every of n  directions, half the vertices lie on one side, and half lie on the other. Its facets are the 2n  hypercubes defined by the vertices on each side in each direction. Alternatively, one can construct each hypercube as the prism of the hypercube of the lower dimension. The prism product of an m -hypercube and an n -hypercube is an (m +n )-hypercube.

Every hypercube can be made regular. As such, the hypercubes comprise one of the three infinite families of polytopes that exist in every dimension, the other two being the simplexes and the orthoplexes (the duals of the hypercubes).

The hypercube is also called the measure polytope. This is because a hypercube with unit edge length has a unit hypervolume, and as such, it can be used to “measure” n -dimensional space like a grid.[1]

Hypercubes can always tile their respective spaces, forming the hypercubic honeycombs.

## Elements

All of the elements of a hypercube are hypercubes themselves. The number of d -dimensional elements of an n -hypercube is given by the binomial coefficient 2n -d C(n ,d ). This is because for each choice of n -d  of the hypercube’s n  directions, and for each of the subsequent 2n d  choices of sides, the vertices on these sides define a unique d -dimensional simplex. In particular, an n -dimensional hypercube has 2n  vertices and 2n  facets, and its vertex figure is the simplex of the previous dimension.

In total, an n -hypercube has 3n  elements, including the nullitope and excluding the bulk of the polytope.

## Examples

Excluding the point, the hypercubes up to 10D are the following:

Rank Name Picture Rank 1 Dyad 6 Hexeract 2 Square 7 Hepteract 3 Cube 8 Octeract 4 Tesseract 9 Enneract 5 Penteract 10 Dekeract

## Vertex coordinates

Coordinates for the vertices of an n -hypercube with edge length 1 are given by:

• ${\displaystyle \left(\pm {\frac {1}{2}},\,\pm {\frac {1}{2}},\,...,\,\pm {\frac {1}{2}}\right)}$

with n entries.

## Measures

• The circumradius of an n -dimensional hypercube of unit edge length is given by ${\displaystyle {\frac {\sqrt {n}}{2}}}$.
• Its inradius is ${\displaystyle {\frac {1}{2}}}$, regardless of n .
• Its height from a facet to the opposite facet is twice the inradius, that is ${\displaystyle 1}$.
• Its hypervolume is ${\displaystyle 1}$, regardless of n .
• The angle between two facet hyperplanes is ${\displaystyle {\frac {\pi }{2}}=90^{\circ }}$, regardless of n .