Polyhedron
A polyhedron is a solid with flat faces (from Greek poly meaning "many" and edron meaning "face").
Each flat surface (or "face") is a polygon.
So, to be a polyhedron there should be no curved surfaces.
Examples of Polyhedra:



Triangular Prism 
Cube 
Dodecahedron 
Common Polyhedra
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 the "Polyhedral Formula", and is very useful to make sure you have counted correctly!
Let's try some examples:
This cube has:
 6 Faces
 8 Vertices (corner points)
 12 Edges


F + V  E = 6+812 = 2 
This prism has:
 5 Faces
 6 Vertices (corner points)
 9 Edges


F + V  E = 5+69 = 2 
