Names of Shapes with Various Number of Sides

Sides	Name
n	N-gon
3	Triangle
4	Quadrilateral
5	Pentagon
6	Hexagon
7	Heptagon
8	Octagon
10	Decagon
12	Dodecagon

According to Yahoo! Ansers, there also proposals for shapes of other number of sides.
多角形の名称です。意外と知らないののですね。