Frank Revi
Tetraprism.net (barely started) is about my work related to variations on the theme of the tetrahedron. A tetrahedron is a 3-dimensional shape (polyhedron) with 4 triangular faces. A regular tetrahedron is one where all four faces are congruent (same-size equilateral triangles). The regular tetrahedron, especially, is well-analyzed. It is a Platonic solid, identified back even before ancient Greece.
Likewise, the mathematical notion of a prism is well-defined and well-understood.
The term “tetraprism” is not a formal mathematical thing (or even official English word). I have adopted it to refer to a class of shapes slightly more general than a prism or a tetrahedron. I define a tetraprism basically as a volume with two parallel, planar, but otherwise arbitrary quadrilateral faces (bases) in the most obvious arrangement – bases concave (no crossing edges), not coplanar, vertices not colinear, etc., with the corresponding vertices connected by edges, so each face connecting the bases is a simple, but not necessarily planar, quadrilateral. More generally (in reductive cases), the bases can have 4, 3, or 2 vertices each. It is possible to formalize this definition mathematically, but not very interesting or relevant.
