Vertex-first projection of a hexadecachoron. In this projection, eight cells are obscured.

A hexadecachoron (also called tetracross) is the four-dimensional cross polytope and the dual of a tesseract. It is also called a 16-cell, due to its 16 tetrahedral cells. It has the schläfli symbol , meaning that 4 tetrahedra meet at each edge. Its Bowers acronym is "hex".


The hexadecachoron is the 4-D demihypercube, meaning it can be constructed by taking half the vertices of a tesseract. It is also a bipyramid of an octahedron, or a square duopyramid. Eight tetrahedra join at each vertex.


When seen from one of its cells, the hexadecachoron first has one cell, then four attached to its faces. The next six share an edge with the top cell and are perpendicular to it. The remaining four side cells share only a vertex with the top cell, and are themselves joined to the final cell, in dual orientation to the top cell.

In vertex-first orientation, it is just two octahedral pyramids joined together.



See also

Zeroth First Second Third Fourth Fifth Sixth Seventh Eighth Ninth Tenth Eleventh Twelfth Thirteenth Fourteenth Fifteenth Sixteenth
Simplex Point Line Triangle Tetrahedron Pentachoron Hexateron Heptapeton Octaexon Enneazetton Decayotton Hendecaxennon Dodecadakon Tredecahendakon Quattuordecadokon Quindecatradakon Sexdecateradakon Septendecapetadakon
Hypercube Point Line Square Cube Tesseract Penteract Hexeract Hepteract Octeract Enneract Dekeract Undekeract Dodekeract Tredekeract Quattuordekeract Quindekeract Sexdekeract
Cross Point Line Square Octahedron Hexadecachoron Pentarss Hexarss Heptarss Octarss Ennearss Decarss Hendecarss Dodecarss Tredecarss Quattuordecarss Quindecatrarss Sexdecaterarss
Hypersphere Point Line Circle Sphere Glome Hyperglome Hexaphere Heptaphere Octaphere Enneaphere Decaphere Hendecaphere Dodecaphere Tredecaphere Quattuordecaphere Quindecatraphere Sexdecateraphere
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