0:04 Hi, everyone! Today we're going to learn about symmetry.

0:10 Symmetry is a concept that is commonly found in math - especially geometry -

0:16 but it is also often discussed in art and design.

0:21 An object that has symmetry can be divided into identical pieces. When an

0:27 object has symmetry, we say that it is symmetrical. When an object does not

0:33 have symmetry, we say that it is asymmetrical.

0:39 There are many different types of geometric symmetry, but today we are only

0:43 going to talk about the simplest form, reflectional symmetry. An object or

0:50 image that has reflectional symmetry is like a mirror image.

0:56 If you were to draw an imaginary line down the center of a symmetrical object

1:00 and fold it in half along that line, the shapes would match up. This

1:06 imaginary line is called a 'line of symmetry.' Some symmetrical objects only

1:12 have one line of symmetry, while others have more.

1:18 For example, this triangle only has one line of symmetry, straight down the

1:24 middle, because if you try to divide it any other way the pieces don't match up.

1:31 This triangle, on the other hand, has three lines of symmetry. You could fold

1:37 it here, here, or here, and each time the halves would be the same.

1:46 A square has four lines of symmetry. You could divide it in half from left to

1:51 right, top to bottom, or from corner to corner either way.

1:59 Symmetry is often found in nature. One favorite example of this is a

2:09 butterfly. When a butterfly folds its wings, it is easy to see that they are

2:19 Now that you know what symmetry means, see if you can find symmetrical

2:24 objects near you. You may be surprised by how many things are symmetrical!