- Angles, Lines, and Polygons
- Home
- Measuring an angle with the protractor
- Acute, obtuse, and right angles
- Naming segments, rays, and lines
- Identifying parallel and perpendicular lines
- Acute, obtuse, and right triangles
- Classifying scalene, isosceles, and equilateral triangles by side lengths or angles
- Finding an angle measure of a triangle given two angles
- Naming polygons
- Drawing and identifying a polygon in the coordinate plane

- Selected Reading
- UPSC IAS Exams Notes
- Developer's Best Practices
- Questions and Answers
- Effective Resume Writing
- HR Interview Questions
- Computer Glossary
- Who is Who

Polygons are 2-dimensional closed shapes made of straight lines.

In this lesson we learn how to name a polygon by its number of sides. This requires that we know the Greek prefixes for numbers and some rules for their use.

For polygons with 3 through 20 sides, we simply add "gon" to the prefixes at the left. For example a polygon with 5 sides is known by the name pentagon which is got by adding a ‘gon’ to Greek prefix ‘penta’ (meaning five). A polygon with three sides is more commonly called a triangle rather than a trigon and a polygon with four sides is more commonly known as a quadrilateral, rather than a tetragon.

Polygon Names | |
---|---|

Sides | Names |

3 | Triangle |

4 | Quadrilateral |

5 | Pentagon |

6 | Hexagon |

7 | Heptagon |

8 | Octagon |

9 | Nonagon |

10 | Decagon |

Name the following polygon based on its number of sides.

**Step 1:**

Given polygon has ten sides.

**Step 2:**

So it is a Decagon.

Name the following polygon based on its number of sides.

**Step 1:**

Given polygon has four sides.

**Step 2:**

So it is a tetragon or quadrilateral.

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