A polyhedron is a solid with flat faces (from Greek poly- meaning "many" and -edron meaning "face").
Each face is a polygon (a flat shape with straight sides).
So, to be a polyhedron there should be no curved surfaces.
Examples of Polyhedra:
Explore 100s of Animated Polyhedron Models.
You can also see some Images of Polyhedra if you want.
Counting Faces, Vertices and Edges
If you count the number of faces (the flat surfaces), vertices (corner points), and edges of a polyhedron, you can discover an interesting thing:
The number of faces plus the number of vertices minus the number of edges equals 2
This can be written neatly as a little equation:
F + V - E = 2
It is known as Euler's Formula (or the "Polyhedral Formula") and is very useful to make sure you have counted correctly!
Let's try some examples:
This cube has:
|F + V - E = 6+8-12 = 2|
This prism has:
|F + V - E = 5+6-9 = 2|
But there are cases where it does not work! Read Euler's Formula for more.
Note: the plural of polyhedron is either polyhedrons or polyhedra