Naming Polygons (3-8 Sides) | Geometry for Kids | Math with Mr. J

Welcome to Math with Mr. J. In this video, I'm going to cover how to name polygons. And remember, a polygon is a shape that is flat, closed, and has straight sides. Now, polygons are named by the number of sides they have. And in this video, we will cover the names of polygons from three sides to eight sides. And I think you'll be familiar with some of these names already, especially the first one here, which we will jump into right now. So let's start with what we call a polygon that has three sides. And here are two examples. A polygon with three sides is called a triangle. Now, there are two triangles here. The top triangle, that's yellow, is a regular polygon, a regular triangle. The green triangle below is an irregular polygon, an irregular triangle. So when we hear regular or irregular, a regular polygon means all of the sides are the same length, and all of the angles are the same measure. An irregular polygon is just a polygon that's not regular. So irregular means that all of the sides are not the same length, or all of the angles are not the same measure, or it can be both of those things, all different sides and all different angles. We will take a look at a regular and an irregular polygon for each kind of polygon we go through. Regular up top, irregular down below. Let's move on to four-sided polygons and take a look at a couple of examples. So, any idea what we call a four-sided polygon? Well, a quadrilateral. Now, you may have thought square, which is a type of quadrilateral. It's a specific quadrilateral. Think, is everything with four sides a square? No. So quadrilateral includes all polygons with four sides, including squares. Now, we have a square there for our regular quadrilateral. All of the sides are the same length and angles are the same measure. Then we have a rectangle for our irregular quadrilateral. All of the angles are the same, 90 degrees, but not all of the sides are the same length. So that is irregular. Let's move on to five-sided polygons and take a look at our examples. Any idea what a five-sided polygon is called? If you thought pentagon, you are correct. And there is a regular and irregular pentagon there. Let's move on to six sides through eight sides. Moving on to six-sided polygons now, let's take a look at a couple of examples. Any idea what we call a six-sided polygon? Well, a hexagon. So there is a regular and an irregular hexagon there. Now, a good way to remember six sides and hexagon match the X's. Six has an X and so does hexagon. Let's move on to seven sides. A seven-sided polygon is called a heptagon. Now, our irregular example here is an interesting one, that arrow. But if you count the sides, you see we have a polygon with seven sides. Now, I do want to mention you may also hear septagon for a seven-sided polygon. So both heptagon and septagon mean a seven-sided polygon. Lastly, we have eight sides. Any idea what an eight-sided polygon is called? Think of an animal that has eight arms. Well, an eight-sided polygon is called an octagon. And the animal with eight arms that can help us remember this is an octopus. So there you have it. There are the names of polygons, three sides through eight sides. I hope that helped. Thanks so much for watching. Until next time, peace.