Polygon

 

 

How are polygons named?

 

Polygons are named according to the number of sides they have. The first part of the word polygon ('poly') means 'any number' and the second part ('gon') means 'straight sides', so a polygon is a two dimensional shape with striaght sides. (forgot all you may have heard about opening the cage door and polly's gone!).

Most of the polygons shown in the diagram are regular polygons with the exception of the quadrilateral. That is, they have all their sides the same length and all their angles the same size. You need to know the names of the polygons from the triangle up to the decagon (10 sides) and the dodecagon (12 sides). Many of the others do have names, but you won't need them for your GCSE maths examination.

The reason we have shown mainly regular polygons is that is the way they are normally used in exam questions, for example 'Find the volume of this prism, when the cross section of the prism is a regular hexagon', but it is important to remember that any shape with six straight sides is a hexagon, even if it is a very irregular one.

Name Number of sides
Triangle 3
Quadrilateral 4
Pentagon 5
Hexagon 6
Heptagon 7
Octagon 8
Nonagon 9
Decagon 10
Dodecagon 12