# Definition:Polygon/Regular

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## Definition

A **regular polygon** is a polygon which is both equilateral and equiangular.

That is, in which all the sides are the same length, and all the vertices have the same angle:

## Also known as

In Euclid's *The Elements*, a **regular polygon** is referred to as an **equilateral and equiangular polygon**.

## Examples

Specific instances of regular polygons with specific numbers of sides are as follows:

- $3$ sides: Equilateral Triangle
- $4$ sides: Square
- $5$ sides: Regular Pentagon
- $6$ sides: Regular Hexagon
- $7$ sides: Regular Heptagon
- $8$ sides: Regular Octagon
- $9$ sides: Regular Nonagon or Regular Enneagon
- $10$ sides: Regular Decagon
- $11$ sides: Regular Hendecagon or Regular Undecagon
- $12$ sides: Regular Dodecagon

- $17$ sides: Regular Heptadecagon

The term **regular $n$-gon** is usually used nowadays to specify a regular polygon with a specific number, that is $n$, sides.

The specific name is usually invoked only in order to draw attention to the fact that such a regular polygon has a particularly interesting set of properties.

## Also see

## Sources

- 1937: Eric Temple Bell:
*Men of Mathematics*... (previous) ... (next): Chapter $\text{IV}$: The Prince of Amateurs - 1992: George F. Simmons:
*Calculus Gems*... (previous) ... (next): Chapter $\text {A}.4$: Euclid (flourished ca. $300$ B.C.) - 2014: Christopher Clapham and James Nicholson:
*The Concise Oxford Dictionary of Mathematics*(5th ed.) ... (previous) ... (next): Entry:**polygon**