as solids: We see solids in terms of what surrounds us—three-dimensional figures
with their surfaces the actual objects we perceive. Geometric solids are actually the
union of the surface and regions of space; in a way, this adds another dimension to
two-dimensional space.
What is a polyhedron?
The word polyhedron comes from the Greek poly(meaning “many”) and the Indo-
European word hedron(meaning “seat”). In geometry, a polyhedron is considered to
be a three-dimensional solid that represents the union of polygonal regions, usually
joined at their edges and having no gaps.
Polyhedrons are classified as convex,or if you extend any side, the figure lies on
only one side of the plane (for example, a pyramid and cube); a concavepolyhedron is
one that can extend on both sides of such a plane (for example, a form that exhibits
concavity on one or all sides of the polyhedron). The plural of polyhedron is often seen
as “polyhedrons,” but it is more correct to use “polyhedra.”
What are the various types of polyhedra?
As with most forms, polyhedra are divided into many names, depending on the num-
ber of faces. The following lists some of them, based on their number of sides:
Types of Polyhedra
Sides Polyhedra Name
4 tetrahedron
5 pentahedron
6 hexahedron
7 heptahedron
8 octahedron
9 nonahedron
10 decahedron
11 undecahedron
12 dodecahedron
14 tetradecahedron
20 icosahedron
24 icositetrahedron
30 triacontahedron
32 icosidodecahedron
60 hexecontahedron
90 enneacontahedron
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