Octagon - Definition with Examples

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What is Octagon?

An octagon is a polygon made up of 8 sides. It has eight angles.


Octagon = Octa + gon where octa means eight and gon means sides. 

There are 20 diagonals in an octagon as shown below.

diagonal octagon


The following figures are not octagons:

heptagon  It is a heptagon as it has seven sides.
pentagon  It is a pentagon as it has five sides.
hexagon  It is a hexagon as it has six sides.
quadrilateral  It is a quadrilateral as it has four sides.


Angles of an octagon:

An octagon consists of 8 angles. The sum of the angles of an octagon is 1080°.

angles of an octagon

In the given octagon, ∠A + ∠B + ∠C + ∠D + ∠E + ∠F + ∠G + ∠H = 1080°.

An octagon has 8 exterior angles. The sum of the exterior angles of an octagon is 360°.

 Regular octagon: An octagon in which all sides and angles are equal. Each angle of a regular octagon is 135°.  Irregular octagon: An octagon in which all sides and all angles are not equal. Measures of angles of an irregular octagon are different but they all sum to 1080°.
regular-octagon irregular octagon


Real life examples

Some of the most popular examples of the octagon are the STOP signboard and umbrella. 

octagon shapes around us


  Fun Facts about octagon

  • The word ‘Octagon’ has been derived from the Greek word ‘ὀκτάγωνον’ (oktágōnon) which means eight angles. This is how the shape with eight angles was named Octagon.

  • During the 1850s and 1900s, many people started building their homes in the shape of an octagon as it is a symbol that represents rebirth, infinity, regeneration, and transition.


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