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# Math geometry vocab

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

Acute triangle | A triangle that measures 89 degree or less. |

Adjacent angles | Two angles that share a common vertex, common side, and do not overlap. |

Base | A prism with at least one of the two parallel congruent faces. |

Center | The middle of the circle. |

Circle | The set of all points in a plane that are the same distance from a given point called the center. |

Circumference | The distance around the circle. |

Complementary angles | Two angles that will equal 90 degree. |

Composite figure | A figure made up of 2 or more shapes. |

Cone | A figure with a circular base connected by a curved side to a single vertex. |

Congruent | Vertical angles that have the same measure. |

Congruent segements | Sides of a triangle with the same length. |

Coplanar | Lines or planes that are connected. |

Cross sections | The intersection of a solid and a plane. |

Cylinder | A 3-D figure with two parallel congruent circular bases connected by a curved surface. |

Diagonal | A line segment that connects two nonconsecutive vertices. |

Diameter | The distance across a circle through it's center. |

Edge | The line segment where two faces of a polyhedron intersect. |

Equilateral triangle | A triangle having three congruent sides. |

Faces | A flat surface of a polyhedron. |

Isosceles triangle | A triangle with at least two congruent sides. |

Lateral face | Any flat surface that is not a base. |

Lateral surface area | The sum of the areas of the lateral faces of a solid. |

Obtuse triangle | A triangle with one obtuse angle (obtuse angle=91+ degree. |

Pi | The ratio of the circumference of a circle to it's diameter. The Greek letter PI represents this number. The value is 3.1415926... or 3.14 or 22/7. |

Plane | A 2-D flat surface that extends in all directions. |

Polyhedron | A 3-D figure with faces that are polygons. |

Prism | A polyhedron with two parallel congruent faces called bases. |

Pyramid | A polyhedron with one base that is a polygon and three or more triangular faces that meet at a common vertex. |

Radius | The distance from the center of a circle to any point on the circle. |

Regular Pyramid | A pyramid whose base is a regular polygon and in which the segment from the vertex to the center of the base is the altitude. |

Right triangle | A triangle having one right angle. |

Scale model | A model used to represent objects that are too large or too small to be built at actual size. |

Scalene triangle | A triangle having no congruent sides. |

Semicircle | Half of a circle. |

Slant height | The height of each lateral face. |

Supplementary angles | Two Angles that add up to 180 degree. |

Surface area | The sum of the areas of all the surfaces (faces) of a 3-D figure. |

Triangle | A figure with three sides and three angles. |

Vertex | The common endpoint of the rays forming the angle. |

Vertical angles | Opposite angles formed by the intersection of two lines. |

Volume | The measure of the space occupied by a solid. |