16-cell

plural 16-cells

1. geometryA four-dimensional polytope, analogous to an octahedron, whose sixteen bounding facets are tetrahedra.

   The remaining 8, as before, are the vertices of the complementary 16-cell (see Figure 9). In Figure 7, these 8 points have been blackened, but not joined, because the 16-cell has longer edges; diameters of octahedral facets of the 24-cell.

   1995, Harold Scott Macdonald Coxeter, “Paper Three: Two Aspects Of The Regular 24-Cell In Four Dimensions”, in F. Arthur Sherk, editor, Kaleidoscopes: Selected Writings of H.S.M. Coxeter, page 32

   2 more examples

   This polytope has 16 tetrahedral cells, and for this reason it is called the 16-cell.[…]The 16-cell has 24 edges that are the diagonals of the 24 square faces of the hypercube. (Since we are selecting alternate vertices of the hypercube, we only get one diagonal for each square face.)

   2002, Gabor Toth, Glimpses of Algebra and Geometry, 2nd edition, page 385

   We will now consider the dual 16-cell. In some ways the 16-cell is a bit easier because it has fewer vertices and edges. But on the other hand the hypercube is perhaps easier to understand intuitively because we can readily (perhaps) see the various cubes of which it is composed.

   2012, John Barnes, Gems of Geometry, 2nd edition, page 76

   Synonyms: 4-orthoplex, 4-demicube, 4-hemicube, demihypercube, demitesseract, hexadecachoron, hexadecahedroid