Naming and classifying polygons
Count the sides — and check whether the shape is regular or irregular.
A polygon is a closed two-dimensional shape made entirely from straight sides. The name comes from the number of sides:
| Sides | Polygon name |
|---|---|
| 3 | Triangle |
| 4 | Quadrilateral |
| 5 | Pentagon |
| 6 | Hexagon |
| 7 | Heptagon |
| 8 | Octagon |
| 9 | Nonagon |
| 10 | Decagon |
Two further classifications:
- Regular: every side and every angle is the same size. A regular triangle is an equilateral triangle; a regular quadrilateral is a square.
- Irregular: not regular — the sides or angles vary.
Quadrilaterals also come with special names:
- Square: all sides equal, four right angles.
- Rectangle: opposite sides equal, four right angles.
- Parallelogram: opposite sides equal and parallel; opposite angles equal.
- Rhombus: all four sides equal; opposite angles equal.
- Trapezium: exactly one pair of parallel sides.
- Kite: two pairs of equal adjacent sides; one pair of equal opposite angles.
- A polygon is a closed shape with straight sides.
- Name a polygon by counting its sides.
- Regular: all sides and angles equal; irregular: not so.
- Quadrilaterals split into squares, rectangles, parallelograms, rhombi, trapezia and kites.