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 |