A solid can consist of flat (i.e. plane) surfaces or curved surfaces or
combinations of both.
Polyhedra
A polyhedron (or planer body) is a solid or hollow body that is
made up entirely of plane
faces and is three-dimensional.
For example, a cuboid is a polyhedron as it is entirely made up of
planes. Planes that make up the cuboid are called its faces.
There are six faces of the cuboid.
The plural of polyhedron is polyhedra. In Greek, poly means many
and hedra means base.
A polyhedron is named after its number of faces. Some polyhedra and
their names are shown below.
A pentahedron has five faces, a hexahedron has six faces and a decahedron
has 10 faces.
Other examples of polyhedra are:
Prisms
A prism is a solid with cross-sections that are parallel to its
base.
The following solid is a prism.
A prism is named according to the shape of the its base (i.e. shape of
its cross-section). So, the solid drawn above is an example of
triangular prism.
Some other prisms are drawn below:
Key Terms
polyhedron, cuboid, faces,
polyhedra, tetrahedron, heptahedron,
enneahedron, octahedron, dodecahedron,
icosahedron, prism, triangular
prism, cross-section, rectangular
prism, hexagonal prism, pentagonal
prism
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