Polygons (Regular Vs. Irregular)

A regular polygon is one that has all sides and all angles equal whereas an irregular polygon is one which has sides and angles that are not equal. A regular polygon is not limited to the number of sides as even a triangle with equal sides can be regular polygon and so is a quadrilateral or a pentagon. The only thing needed to be called as a polygon is the sides and angles need to be equal.

Regular Polygon

Let’s look at some of the attributes of a regular polygon:


The corner of a polygon is called as the vertex and, in any polygon, the number of corners or vertices and the number of sides are all equal. For example, a square contains 4 corners and 4 sides

Apothem (inradius):

The Apothem is nothing but a line from the center of a regular polygon to the midpoint of any side. It can also be the radius of the incircle, if you imagine drawing a circle inside the polygon.

Radius (circumradius):

The circumradius or the radius is the distance between the center of the polygon to any corner of the polygon. If you draw a circle inside the polygon, the radius of the circumcircle is the circumradius of the polygon.

Central Angle:

The angle at the center of the polygon made by two adjacent radius lines.


A regular polygon has sides of equal length hence the perimeter of a polygon is the length of any side multiplied by number of sides in a polygon.

Area of a regular polygon:

The number of square units it takes to completely fill a regular polygon.

regular polygon


Irregular Polygon

An irregular polygon is just the opposite of a regular polygon as it won’t sides and angles that are equal. But it can be either convex or concave. Some examples of irregular polygon includes scalene triangle, rectangle, irregular hexagon, parallelogram.

irregular polygon