# Polygons: How Many Sides?

A geometrical figure with three or more sides is called a **polygon** or a **polyhedron.** Here are the names for some polygons.

3 | triangle, trigon |

4 | quadrilateral, tetragon |

5 | pentagon |

6 | hexagon |

7 | heptagon |

8 | octagon |

9 | nonagon, enneagon |

10 | decagon |

11 | hendecagon |

12 | dodecagon, duodecagon |

13 | triskaidecagon, tridecagon |

14 | tetrakaidecagon, tetradecagon |

15 | pentadecagon |

16 | hexadecagon |

17 | heptadecagon |

18 | octadecagon |

19 | enneadecagon |

20 | icosagon |

### How Many Angles?

A polygon has **as many angles as it has sides.** For example, a triangle has 3 sides and 3 angles. A pentagon has 5 sides and 5 angles. An octadecagon has 18 sides and 18 angles!

Finding Perimeter and Circumference | Numbers and Formulas | Decimal Equivalents of Common Fractions |

**See also:**