What is Symmetry?

Symmetry is a concept that is commonly found in math – especially geometry but it is also often discussed in art and design. An object that has symmetry can be divided into identical pieces. When an object has symmetry, we say that it is symmetrical. When an object does not have symmetry, we say that it is asymmetrical. There are many different types of geometric symmetry, but today we are only going to talk about the simplest form, reflectional symmetry. An object or image that has reflectional symmetry is like a mirror image.

If you were to draw an imaginary line down the center of a symmetrical object and fold it in half along that line, the shapes would match up. This imaginary line is called a ‘line of symmetry.’ Some symmetrical objects only have one line of symmetry, while others have more. For example, this triangle only has one line of symmetry, straight down the middle, because if you try to divide it any other way the pieces don’t match up. This triangle, on the other hand, has three lines of symmetry. You could fold it here, here, or here, and each time the halves would be the same. A square has four lines of symmetry. You could divide it in half from left to right, top to bottom, or from corner to corner either way. Symmetry is often found in nature. One favourite example of this is a butterfly. When a butterfly folds its wings, it is easy to see that they are the same shape. Now that you know what symmetry means, see if you can find symmetrical objects near you. You may be surprised by how many things are symmetrical!