A list of the more important polygons is given below. A polygon is a 2D shape that consists only of straight sides. The name of the type of polygon depends on the number of sides.
A regular polygon has sides of equal length, and a triangle and rectangle have special names when these polygons are regular.
| Sides | Name | Regular |
| 3 | Triangle | Equilateral triangle |
| 4 | Quadrilateral | Square |
| 5 | Pentagon | |
| 6 | Hexagon | |
| 7 | Heptagon | |
| 8 | Octagon | |
| 9 | Nonagon | |
| 10 | Decagon |
What is the name of a regular 3-sided polygon?
Note that the only regular triangle is an equilateral triangle.
Answer: Equilateral Triangle
If a 20p piece had straight edges, what type of polygon would it be?
A 20p piece has seven edges.
Answer: Heptagon