Adjective
Having five corners or angles.
Source: Webster's dictionaryA regular icosahedron is a gyroelongated pentagonal bipyramid and a biaugmented pentagonal antiprism in any of six orientations. Source: Internet
For example, the small stellated dodecahedron has 12 pentagram faces with the central pentagonal part hidden inside the solid. Source: Internet
Cmain tends to avoid having double bonds in the pentagonal rings, which makes electron delocalization poor, and results in Cmain not being " superaromatic ". Source: Internet
Halides Protactinium(V) fluoride forms white crystals where protactinium ions are arranged in pentagonal bipyramids and coordinated by 7 other ions. Source: Internet
In mathematical terms, the structure of a fullerene is a trivalent convex polyhedron with pentagonal and hexagonal faces. Source: Internet
In this nomenclature, an octahedron would be a square bipyramid, a cuboctahedron would be a triangular gyrobicupola, and an icosidodecahedron would be a pentagonal gyrobirotunda. Source: Internet