polygon names — Definition, Formula & Examples
Polygon names are the standard labels given to polygons based on their number of sides. Each name comes from a Greek (or Latin) prefix for the side count, combined with the suffix '-gon,' meaning angle.
A polygon with sides is named by attaching the Greek numerical prefix corresponding to to the suffix '-gon.' For commonly referenced values of (3 through 12, and select higher values), these names are standardized in mathematics. For large or uncommon values, the polygon is typically referred to as an '-gon.'
How It Works
To find the name of a polygon, count its sides and match the number to its Greek prefix. Here is the standard list:
| Sides | Name |
|---|---|
| 3 | Triangle |
| 4 | Quadrilateral |
| 5 | Pentagon |
| 6 | Hexagon |
| 7 | Heptagon |
| 8 | Octagon |
| 9 | Nonagon |
| 10 | Decagon |
| 11 | Hendecagon |
| 12 | Dodecagon |
For polygons with more than 12 sides, you can use the -gon convention — for example, a 15-sided polygon is simply called a 15-gon. Some larger polygons do have accepted names (e.g., icosagon for 20 sides), but using '-gon' is always valid.
Worked Example
Problem: A floor tile has 8 equal sides. What is the name of this polygon, and what is the sum of its interior angles?
Identify the name: Count the sides: 8. The polygon with 8 sides is called an octagon.
Find the angle sum: Use the interior angle sum formula with n = 8.
Answer: The tile is an octagon, and the sum of its interior angles is .
Why It Matters
Knowing polygon names lets you communicate precisely in geometry problems and standardized tests. Architects, engineers, and game designers routinely reference hexagons, octagons, and other named shapes when describing structures, tiles, and game boards.
Common Mistakes
Mistake: Confusing a hexagon (6 sides) with a heptagon (7 sides) or an octagon (8 sides).
Correction: Learn the Greek prefixes: 'hex-' means 6, 'hept-' means 7, 'oct-' means 8. Associating each prefix with a familiar object (e.g., an octopus has 8 arms) can help.