World Library  
Flag as Inappropriate
Email this Article


Article Id: WHEBN0018422403
Reproduction Date:

Title: Vertex-transitive  
Author: World Heritage Encyclopedia
Language: English
Subject: Polyhedron, Polyhedral compound, Hexagram, Tiling by regular polygons, Final stellation of the icosahedron, Isotoxal figure
Publisher: World Heritage Encyclopedia


(D4 symmetry)
Blue and red lines of reflection are drawn

In geometry, a polytope (a polygon, polyhedron or tiling, for example) is isogonal or vertex-transitive if, loosely speaking, all its vertices are the same. That implies that each vertex is surrounded by the same kinds of face in the same or reverse order, and with the same angles between corresponding faces.

Technically, we say that for any two vertices there exists a symmetry of the polytope mapping the first isometrically onto the second. Other ways of saying this are that the group of automorphisms of the polytope is transitive on its vertices, or that the vertices lie within a single symmetry orbit.

The term isogonal has long been used for polyhedra. Vertex-transitive is a synonym borrowed from modern ideas such as symmetry groups and graph theory.

It is important to note that the pseudorhombicuboctahedron — which is not isogonal — demonstrates that simply asserting that "all vertices look the same" is not as restrictive as the definition used here, which involves the group of isometries preserving the polyhedron or tiling.

2 dimensions: Isogonal polygons

All regular polygons and regular star polygons are isogonal.

Some even-sided polygons which alternate two edge lengths, for example rectangle, are isogonal.

All such 2n-gons have dihedral symmetry (Dn, n=2,3,...) with reflection lines across the mid-edge points.

3 dimensions: Isogonal polyhedra

Isogonal polyhedra may be classified:

  • Regular if it is also isohedral (face-transitive) and isotoxal (edge-transitive); this implies that every face is the same kind of regular polygon.
  • Quasi-regular if it is also isotoxal (edge-transitive) but not isohedral (face-transitive).
  • Semi-regular if every face is a regular polygon but it is not isohedral (face-transitive) or isotoxal (edge-transitive). (Definition varies among authors; e.g. some exclude solids with dihedral symmetry, or nonconvex solids.)
  • Uniform if every face is a regular polygon, i.e. it is regular, quasiregular or semi-regular.
  • Noble if it is also isohedral (face-transitive).

An isogonal polyhedron has a single kind of vertex figure. If the faces are regular (and the polyhedron is thus uniform) it can be represented by a vertex configuration notation sequencing the faces around each vertex.

N dimensions: Isogonal polytopes and tessellations

These definitions can be extended to higher dimensional polytopes and tessellations. Most generally, all uniform polytopes are isogonal, for example, the uniform polychorons and convex uniform honeycombs.

The dual of an isogonal polytope is called an isotope which is transitive on its facets.

k-isogonal figures

A polytope or tiling may be called k-isogonal if its vertices form k transitivity classes.

hexagons. hexagonal faces.
2-isogonal 9/4 enneagram

A more restrictive term, k-uniform figures is defined as an k-isogonal figure constructed only from regular polygons. They can be represented visually with colors by different uniform colorings.

See also


  • Peter R. Cromwell, Polyhedra, Cambridge University Press 1997, ISBN 0-521-55432-2, p. 369 Transitivity
  • (p. 33 k-isogonal tiling, p. 65 k-uniform tilings)

External links

  • MathWorld.
  • Transitivity at Glossary for Hyperspace.
  • Isogonal at Glossary for Hyperspace.
  • Isogonal Kaleidoscopical Polyhedra Vladimir L. Bulatov, Physics Department, Oregon State University, Corvallis, Presented at Mosaic2000, Millennial Open Symposium on the Arts and Interdisciplinary Computing, 21–24 August 2000, Seattle, WA
  • Steven Dutch uses the term k-uniform for enumerating k-isogonal tilings
  • List of n-uniform tilings
  • MathWorld. (Also uses term k-uniform for k-isogonal)
This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.

Copyright © World Library Foundation. All rights reserved. eBooks from Project Gutenberg are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.