In geometry, the triangular dipyramid (or bipyramid) is one of the Johnson solids (J₁₂). As the name suggests, it can be constructed by joining two tetrahedra along one face. It is a convex deltahedron. Although all its faces are congruent and the solid is face-uniform, it is not a Platonic solid because some vertices adjoin three faces and others adjoin four.

The 92 Johnson solids were named and described by Norman Johnson in 1966.

External link

• Johnson Solid -- from MathWorld

Johnson solids | Deltahedra

Diamant triangulaire | 双三角錐