---
tag: 8VEFWD3EJB
kind: concept
name: Polygon
msc: [51M04, 52B05]
sources:
  - url: https://en.wikipedia.org/wiki/Polygon
same_as:
  wikidata: Q37555
  wikipedia: Polygon
---

## Summary

A polygon is a plane figure bounded by a closed chain of finitely many straight segments.
The segments are its edges and their endpoints are its vertices.
Triangles, quadrilaterals and [[regular polygons|01KJJ9A400]] are polygons.
Polygons are the basic building blocks for area, triangulation and much of discrete geometry.

## Explanations

### L1 human

Put some dots on a sheet of paper and join them in order by straight lines, coming back to the first dot at the end.
The closed path you draw is a polygon.
A square with corners $(0, 0)$, $(1, 0)$, $(1, 1)$, $(0, 1)$ is a polygon with four edges.
If the path never crosses itself, the polygon encloses a single region of the plane.