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# Geometry Vocabulary

### Seventh Grade Geometry Vocabulary

Term | Definition |
---|---|

Acute Angle | An angle whose measure is in between 0 and 90 degrees. |

Obtuse Angle | An angles whose measure is in between 90 and 180 degrees. |

Straight Angle | An angle whose measure is exactly 180 degrees. |

Right Angle | An angle whose measure is exactly 90 degrees. |

Complementary Angles | When two angles have a sum of 90 degrees. |

Supplementary Angles | When two angles have a sum of 180 degrees. |

Vertical Angles | When two angles are formed by intersecting lines, are directly across from each other, and are congruent. |

Adjacent Angles | When angles are next to each other. |

Acute Triangle | A triangle whose angles measure 85, 15, and 80 degrees. |

Obtuse Triangle | A triangle whose angles measure 110, 24, and 46 degrees. |

Right Triangle | A triangle whose angles measure 62, 90, and 28 degrees. |

Scalene Triangle | A triangle that has no congruent side lengths. |

Isosceles Triangle | A triangle that has at lease two congruent sides. |

Equilateral Triangle | A triangle that has three congruent sides. |

Quadrilateral | A general name for a four-sided closed figure where all sides are line segments (no curves). |

Rectangle | A quadrilateral with four 90 degree angles. |

Square | A quadrilateral with four 90 degree angles and four congruent sides. |

Parallelogram | A quadrilateral with two pairs of parallel sides. |

Rhombus | A quadrilateral with four equal sides. |

Trapezoid | A quadrilateral with exactly one pair of parallel sides. |

Pentagon | A polygon with five sides. |

Hexagon | A polygon with six sides. |

Heptagon | A polygon with seven sides. |

Octagon | A polygon with eight sides. |

Nonagon | A polygon with nine sides. |

Decagon | A polygon with ten sides. |

Undecagon | A polygon with eleven sides. |

Dodecagon | A polygon with twelve sides. |

Perimeter | The linear distance around the outside side lengths of a figure. |

Area | The amount of squared units that covers the space of a two-dimensional figure. |

Surface Area | The amount of squared units that cover the area of the faces of a three-dimensional figure. |

Volume | The amount of cubic units that fill the inside space of a three-dimensional figure. |