# Video: Naming Polygons

In this video, we will learn how to count the edges and vertices of polygons in order to name them as triangles, quadrilaterals, pentagons, hexagons, or octagons.

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### Video Transcript

Naming Polygons

In this video, we will learn how to count the sides and vertices of polygons to identify whether or not they’re a triangle, a quadrilateral, a pentagon, a hexagon, or an octagon.

Polygons are shapes with straight sides. Which of these two groups of shapes have straight sides? This shape has straight sides. This shape also has straight sides. All of the shapes in this group have straight sides. We can call this group polygons. The shapes in the second group have curved sides or some curved sides. These shapes are not polygons.

There are different types of polygon. To help us identify polygons, we can count the number of sides and the number of corners. Each of these polygons has three sides. They also have three corners. The corners or vertices are where two sides meet. A shape with three sides and three corners is called a triangle. All of these polygons have four sides and four corners.

We call four-sided shapes quadrilaterals. We call shapes with five sides and five corners or vertices pentagons. We call polygons with six sides and six corners hexagons. And we call polygons with eight sides and eight corners octagons. An octopus has eight legs. This is a good way to remember an octagon has eight sides. Let’s try some questions to help us practice identifying different polygons by the number of sides and corners.

How many vertices are there in a triangle?

In this question, we’re asked how many vertices a triangle has. A vertex is another word for corner, and it’s the point where two lines meet. Let’s draw a triangle to help us answer the question. How many sides does a triangle have? One, two, three. Let’s count the number of corners or vertices. There’s one, two, Three. There are three vertices in a triangle.

What is the name of a six-sided polygon?

We have to name the polygon with six sides. Polygons are shapes made from straight sides, so a six-sided polygon has six straight sides. Let’s sketch a six-sided shape. One, two, three, four, five, six. A six-sided polygon is called a hexagon.

What is the name of this shape? Is it an octagon, a pentagon, a quadrilateral, a triangle, or a hexagon?

An octagon is a shape with eight sides. A pentagon is a shape with five sides. A quadrilateral is a four-sided shape. Triangles have three sides, and hexagons have six. How many sides does this shape have? One, two, three, four, five. Which shape has five sides? It’s the pentagon. A polygon with five sides is called a pentagon. The name of this shape is a pentagon.

How many more sticks does Matthew need to change this hexagon into an octagon?

We know that Matthew has made a hexagon using his sticks. And the question is asking us how many more sticks will he need to make an octagon. This question is asking us to think about how many sides a hexagon has and how many sides an octagon has. Hexagons, including Matthew’s hexagon, have six sides. An octagon has eight sides. What’s the difference between eight and six? The answer is two. Eight subtract six is two. Matthew will need two more sticks to change his hexagon into an octagon.

True or false? The number of sides of a polygon is equal to the number of vertices.

This question is asking us to think about polygons. We’re being asked if the number of sides a polygon has is the same as the number of vertices it has. Let’s draw some polygons to help us think about the question. A triangle is a polygon with three sides and three corners. So, this polygon has an equal number of sides and vertices.

Quadrilaterals have four sides and four corners. The number of sides and vertices are equal. Pentagons are polygons with five sides and five corners. The number of sides and vertices is equal. A hexagon is a polygon with six sides and six corners. The number of sides and the number of vertices or corners is equal. And an octagon is a polygon with eight sides and eight corners or vertices. The number of sides is equal to the number of vertices. This statement is true. The number of sides of a polygon is equal to the number of vertices.

What have we learned in this video? We’ve learned that polygons are shapes made from straight sides. And we can identify polygons by counting the number of sides or vertices.