Pyramids (geometry)

geometrical shape

thumb|A tetrahedron.

pyramid having a square base

pyramid having a pentagonal base

Johnson solid

Johnson solid

In geometry, the 5-cell is the convex 4-polytope with Schläfli symbol {3,3,3}. It is a 5-vertex four-dimensional object bounded by five tetrahedral cells. It is also known as a C5, hypertetrahedron, pentachoron, pentatope, pentahedroid, tetrahedral pyramid, or 4-simplex (Coxeter's \alpha_4 polytope), the simplest possible convex 4-polytope, and is analogous to the tetrahedron in three dimensions and the triangle in two dimensions. The 5-cell is a 4-dimensional pyramid with a tetrahedral base and four tetrahedral sides.

Johnson solid

10th Johnson solid (13 faces)

Johnson solid

polyhedron with 7 faces

polyhedron constructed by adjoining an pyramid to a prism