Polygon

Generally, the word polygon is used to refer to a two dimensional construction that encloses a space using straight lines. Regular polygons have sides that are of equal length and have equal angles between each side. [Concave polygon]?s have at least one internal angle that is greater than 180°, whereas convex polygons have all internal angles less than 180°. A cyclic polygon has all of its vertexes lying on the same circle. A polygon can belong to several classifications simultaneously; a square is a regular, convex, cyclic polygon, for example.

'Poly-' is from the Greek word for 'many' and '-gon' is a Greek combining form meaning 'angle'. Strictly speaking, every polyhedron is also a polygon as is every polytope, since they all have angles.

Regular Polygons

Name	Sides	Angle*
Triangle	3	60°
Square	4	90°
Pentagon	5	108°
Hexagon?	6	120°
Septagon	7	128.57°
Octagon	8	135°
Nonagon	9	140°
Decagon	10	144°
Hectagon	100	176.4°
Megagon	106	180.° (approx.)
Googolgon	10100	180.° (approx.)

 * Angle= 180°-(360°/ Sides )