Trigonal trapezohedron120px|Trigonal trapezohedronTypetrapezohedronConway notationCoxeter diagramFaces6 rhombiEdges12Vertices8Face configurationSymmetry group order 12Rotation group order 6Dual polyhedrontrigonal antiprismPropertiesconvex, equilateral polygon, face-transitive, zonohedron, parallelohedron

In chemistry, trigonal planar is a molecular geometry model with one atom at the center and three atoms at the corners of an equilateral triangle, called peripheral atoms, all in one plane.

In chemistry, a trigonal bipyramid formation is a molecular geometry with one atom at the center and 5 more atoms at the corners of a triangular bipyramid.

In chemistry, a trigonal pyramid is a molecular geometry with one atom at the apex and three atoms at the corners of a trigonal base, resembling a tetrahedron (not to be confused with the tetrahedral geometry).