Polyhedron
Polyhedron  

About  
Rank  3  
Plural  Polyhedra  
Facet name  Face  
Counts  
Regular convex polyhedra  5  
Regular star polyhedra  4  
Regular finite compounds  1  
Regular tesselations  3  
Regular finite skew polyhedra of full rank  9  
Regular skew apeirotopes  27  
Hierarchy  

A polyhedron or 3polytope is a polytope of rank 3. The facets of polyhedra are polygons, which are called its faces.
Definition
Polyhedra can be defined to be polytopes of rank 3, however there is no universal agreedupon definition of a polyhedron since the meaning of what a polytope is will differ depending on the context. In nearly all cases, polyhedra will have the structure of an abstract polytope, but sometimes this is not required (as an example, holyhedra do not have the abstract structure of a polyhedron).
The term polyhedron may occasionally be used as a synonym for polytope. For example associahedra, despite its suffix, are not necessarily rank 3.
A polyhedron compound is a compound of rank 3, or equivalently an arrangement of polyhedra.
Regular polyhedra
A regular polyhedron is a polyhedron whose flags are identical under its symmetry group. All regular polyhedra are uniform, isogonal, isotoxal, isohedral, and noble. In 3D Euclidean space, there are 9 finite regular polyhedra and 3 tilings that are not skew, 9 finite skew polyhedra, and 27 regular skew apeirohedra.
External links
 Wikipedia contributors. "Polyhedron".
 Weisstein, Eric W. "Polyhedron" at MathWorld.
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