4-Sided Polygons

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  • 0:03 What Is a Quadrilateral?
  • 0:30 Parallelograms
  • 0:56 Rectangles and Squares
  • 1:52 Rhombuses and Kites
  • 2:27 Trapezoids
  • 2:55 Lesson Summary
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Lesson Transcript
Instructor: Lisa Hanson

Lisa is a Continuous Improvement Coach for her school district and has taught in elementary school for many years. She has a master's degree in curriculum and instruction.

We are shaping up and talking about quadrilaterals. In this lesson, you'll learn about the different kinds of four-sided polygons and their properties. Let's see if we can keep them all straight!

What Is a Quadrilateral?

Everywhere you look there are polygons, closed shapes that have only straight lines. Polygons that have four sides and four angles are called quadrilaterals. They are found in many things around us: doors, windows, books, TVs, pictures, etc. There are six types of quadrilaterals. Once you learn them, you will be amazed at how often you spot them. The picture will help identify each shape as it is described.

Quadrilateral Shapes


A parallelogram is easy to remember because its name says it all. It is a quadrilateral with two sets of parallel sides, simple as that. Shapes A, B, C, and E in the picture can all be called parallelograms because their opposite sides are parallel. You can find them all around you, from floor patterns, to windows, to some shapes of food. Many four-sided polygons are called parallelograms, but also have more specific names.

Rectangles and Squares

One of the most well-known quadrilaterals, which is also a parallelogram, is a rectangle. A rectangle has two sets of parallel sides and all four angles are right angles ( or 90° angles), which are its special properties. The opposite sides of a rectangle are always equal in length. Shapes A and C can be called rectangles. Think of three things in your life that are rectangles. A desk or book would be the shape of a rectangle.

The most recognizable of all quadrilaterals is the square. It is one of the first shapes we learn as a child. A square is also a parallelogram, a rhombus, and a rectangle because it has all of those properties as well. A square has two sets of parallel lines, all lines are equal, and all angles are right angles. It must have all of these things to be a square. Shape A is an example of a square. Now let's move onto a couple quadrilaterals that aren't parallelograms.

Rhombuses and Kites

A rhombus is a very simple quadrilateral. It has two sets of parallel sides, and all sides are equal. That is it. We don't worry about the angles with a rhombus. Shapes A and B are examples of a rhombus.


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