Flat shapes are all around you. A window can be a square, a slice of naan can be a triangle, and a coin is a circle. These are called 2D shapes because they are flat.
Why this matters: When you can name shapes and count their sides and corners, you can describe the world neatly. This helps with drawing, building and reading maps later on.
Sides and corners
A side is a straight edge. A corner (also called a vertex) is where two sides meet. Let's count them.
| Shape | Sides | Corners |
|---|---|---|
| Triangle | 3 | 3 |
| Square | 4 | 4 |
| Rectangle | 4 | 4 |
| Pentagon | 5 | 5 |
| Hexagon | 6 | 6 |
| Circle | 0 (one curved edge) | 0 |
Regular and irregular
A regular shape has all sides the same length and all corners the same. A irregular shape has sides or corners that are different sizes.
A square is a regular rectangle: every side is equal. A long, thin rectangle is irregular, because two sides are long and two are short.
Above you can see a square, a triangle and a circle side by side.