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# Polygons Vocab.

### Polygons and Quadrilaterals vocabulary (Geometry - Mrs. Davis)

term | definition |
---|---|

acute angle | angle less than ninety degrees |

acute triangle | triangle with all angles less than ninety degrees |

angle | two rays with a common endpoint |

complementary | adjective describing two angles whose sum is ninety degrees |

congruent | adjective describing figures with the same shape and size |

decagon | ten-sided polygon |

degree | unit of measure for angles (the most common) |

dilation | a type of transformation: the process of reducing or enlarging a figure |

inductive reasoning | a rule based on a pattern of several examples |

deductive reasoning | reasoning in which the conclusion is reached from previously known facts |

equilateral | all sides of a figure are congruent |

heptagon | seven-sided polygon |

hexagon | six-sided polygon |

indirect measurement | Indirect measurement is a technique that uses proportions to find a measurement when direct measurement is not possible. |

inscribed polygon | a polygon whose vertices rest on the circle |

isosceles | adjective for a polygon with two congruent sides |

line of symmetry | the fold line between two halves that mirror each other |

line symmetry | figures that match exactly when folded in half have line symmetry |

nonagon | nine-sided polygon |

obtuse angle | an angle measuring more than ninety degrees but less than 180 degrees |

obtuse triangle | a triangle containing one obtuse angle |

octagon | eight-sided polygon |

pentagon | five-sided polygon |

polygon | a simple closed figure formed by three or more line segments |

simple | adjective meaning that line segments do not cross each other |

protractor | a tool used to measure angles |

quadrilateral | four-sided polygon |

reflection | a mirror image of a figure across a line of symmetry |

regular polygon | a polygon with all sides congruent and all angles congruent |

rhombus | an equilateral quadrilateral |

right angle | an angle measuring exactly ninety degrees |

right triangle | a triangle containing a ninety degree angle |

scalene | adjective for a triangle with three unequal sides |

similar | adjective for polygons having corresponding angles congruent and corresponding sides in porportion |

straight angle | angle containing 180 degrees |

supplementary | adjective for two angles whose sum is exactly 180 degrees. |

tessellation | a repetitive pattern of polygons that fit together with no overlaps or gaps |

transversal | a line that intersects parallel lines |

trapezoid | a quadrilateral with exactly one pair of parallel sides |

triangle | a three-sided polygon |

vertex | the common endpoint where line segments or rays meet forming an angle |

translation | one type of transformation where a figure is slid vertically, horizontally, or both |