What is an Irregular Polygon? - Definition & Shapes

An error occurred trying to load this video.

Try refreshing the page, or contact customer support.

Coming up next: How to Find the Area of Irregular Polygons

You're on a roll. Keep up the good work!

Take Quiz Watch Next Lesson
Your next lesson will play in 10 seconds
  • 0:00 Polygons
  • 0:49 Irregular Polygons
  • 1:27 N-Sided Regular and…
  • 3:06 Example
  • 3:57 Lesson Summary
Save Save Save

Want to watch this again later?

Log in or sign up to add this lesson to a Custom Course.

Log in or Sign up

Speed Speed Audio mode

Recommended Lessons and Courses for You

Lesson Transcript
Instructor: Laura Pennington

Laura received her Master's degree in Pure Mathematics from Michigan State University. She has 15 years of experience teaching collegiate mathematics at various institutions.

Polygons show up often in the world around us. This lesson will define regular and irregular polygons and teach us to distinguish between the two. We will become familiar with different n-sided polygons and their shapes.


Did you know that when you are writing on a piece of paper, you are writing on a polygon, or that when you are looking at certain street signs, you are looking at a polygon? A polygon is a two-dimensional shape with at least three sides that are straight and create interior angles where they meet. They show up all the time in the world around us.

Polygons can be regular or irregular. In order to define an irregular polygon, we must first look at regular polygons. A regular polygon is a polygon with all sides of equal length and all interior angles of equal measure. For example, a yield street sign is a regular polygon with three sides.

Now that we understand what a regular polygon is, we can move on to what this lesson is all about: irregular polygons.

Irregular Polygons

An irregular polygon is a polygon that is not regular. That is, an irregular polygon is a polygon that does not have all sides of equal lengths and all interior angles equal. For example, consider this picture of an SD card:

5-sided Irregular Polygon

Notice the SD card has 5 sides and they are not all equal length. Also, the interior angles are not all equal. Therefore, the SD card takes on the shape of an irregular polygon.

These are all things that you may come across on a daily basis. Isn't it neat how mathematics can make us look at the world around us so differently when we learn something new?

N-Sided Regular and Irregular Polygons

Notice that the polygons that we've given examples of all have a different number of sides. Polygons can have any number of sides as long as there are three or more of them. A lot of n-sided polygons have special names. For example, a piece of paper has four sides, and we call it a quadrilateral. The yield sign has three sides, and we call it a triangle. Lastly, the SD card has five sides, and we call it a pentagon.

The special names we give polygons with certain numbers of sides can either be regular or irregular. For instance, the yield sign was a regular polygon with three sides. As we said, a polygon with three sides is called a triangle. Thus, we would call the yield sign a regular triangle. Similarly, the SD card is called a pentagon because it has five sides. Since it is irregular, we would call it an irregular pentagon.

Let's go through some other kinds of polygons with special names. So, the first one we already know. A polygon with three sides is a triangle. A polygon with four sides is called a quadrilateral and one with five sides, we already know that's a pentagon. A polygon with six sides is referred to as a hexagon, one with seven sides is called a heptagon, and, finally, a polygon with eight sides is an octagon.

To unlock this lesson you must be a Member.
Create your account

Register to view this lesson

Are you a student or a teacher?

Unlock Your Education

See for yourself why 30 million people use

Become a member and start learning now.
Become a Member  Back
What teachers are saying about
Try it risk-free for 30 days

Earning College Credit

Did you know… We have over 200 college courses that prepare you to earn credit by exam that is accepted by over 1,500 colleges and universities. You can test out of the first two years of college and save thousands off your degree. Anyone can earn credit-by-exam regardless of age or education level.

To learn more, visit our Earning Credit Page

Transferring credit to the school of your choice

Not sure what college you want to attend yet? has thousands of articles about every imaginable degree, area of study and career path that can help you find the school that's right for you.

Create an account to start this course today
Try it risk-free for 30 days!
Create an account