Classifying Plane Figures

Contributor: Elephango Editors. Lesson ID: 10619

Shape up with this lesson! You'll review plane shapes through interactive online and hands-on activities. There is also a worksheet to show your knowledge of shapes.


Plane Geometry (2D)

learning style
personality style
Grade Level
Intermediate (3-5)
Lesson Type
Skill Sharpener

Lesson Plan - Get It!


Look at the images below.

  • How many different shapes can you identify in each?

Plane figures are flat figures that can be drawn on a surface, such as squares, rectangles, triangles, and circles.

  • Were you able find a lot of them in the images above?

Good job!

  • Did you know they're made of line segments and can be closed or open?

Watch the video Plane Figures| Maths for Kids| Grade 3 by Periwinkle to learn more!

While you're watching, write down your answers to these questions:

  • What is a plane?
  • What do we call the shapes drawn on a plane?
  • What are the 2 types of plane figures?
  • How can we tell if a figure is open?
  • Is a curve open or closed?
  • Is an angle open or closed?
  • How can we tell if a figure is closed?
  • What is the name of point where 2 sides meet?

Let's practice identifying open and closed figures!

We can classify these figures (sort them into groups) by:

  • whether they're open or closed
  • the number of sides
  • the number of vertices
  • whether the side lengths are the same or different

You learned that the place where two sides meet are called vertices. (One is a vertex; two or more are vertices.)

Let's look at some figures, and see how many sides and vertices they have:


A flat, closed shape, with straight sides, is called a polygon. Many different shapes are polygons. Their sides may be equal, or not.

  • Is a circle a polygon?

No. It is flat and closed, but it doesn't have straight sides.

Let's learn more about polygons by watching Naming Polygons- Maths Tutorials from missnorledge.


A rhombus is a flat shape with 4 equal sides.

  • Wait, isn't that what we call a square?

Yes, a square is a rhombus with equal angles. But the angles of a rhombus don't have to be equal.

Here's what a rhombus looks like:


If you said, "Hey, that's a diamond!" you are correct. A diamond shape is a rhombus.


Just one more shape to learn, and that is a trapezoid. A trapezoid is a quadrilateral.

  • Do you remember what that is?

Yes, it's a 4-sided figure.

A trapezoid's special feature is that it only has one set of parallel sides. The other sides are not parallel.


Wow! You learned a lot about plane figures, and even met some strange figures with funny names.

  • Are you ready to practice what you learned?

Great! Move on to the Got It? page, where you'll get to draw all these shapes and practice identifying them!

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