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# Geometry Vocabulary

### geometry terms

Question | Answer |
---|---|

Acute Angle | An angle with a measure greater than 0 degrees but less than 90 degrees. |

Acute Triangle | A triangle with three acute angles |

Angle | Two rays that share an endpoint (vertex) |

Area | The amount of surface in a region or enclosed within a boundary. |

Circle | A closed curve with all points an equal distance from the center |

Circumference | The distance around the outside of a circle. |

Cone | A three-dimensional figure with a circular base joined to a vertex by a curved surface. |

Congruent | Having exactly the same size and shape. |

Cube | A solid figure in which every face is a square and every edge is the same length. |

Decagon | A polygon with ten sides. |

Diameter | A line segment that cuts a circle in half. |

Endpoint | The point(s) at the end of a ray or line segment. |

Equilateral Triangle | A triangle with three congruent sides. Each angle measures 60 degrees. |

Flip | another word for REFLECTION |

Geometry | The branch of mathematics that deals with the position, size, and shape of figures. |

Hemisphere | Half of a sphere |

Heptagon | A polygon with seven sides. |

Hexagon | A polygon with six sides. |

Isosceles Triangle | A triangle with at least two congruent sides and two congruent angles. |

Kite | A convex quadrilateral with two distinct pairs of adjacent, congruent sides. |

Line | A set of points that form a straight path extending infinitely in two directions. |

Line of Symmetry | A line dividing a two-dimensional figure into two parts that are mirror images of each other. |

Line Segment | A part of a line. A line segment has two endpoints and a definite length. |

Nonagon | A polygon with nine sides. |

Obtuse Angle | An angle that is greater than 90 degrees but less than 180 degrees |

Obtuse Triangle | A triangle that has one obtuse angle. |

Octagon | A polygon with eight sides. |

Parallel Lines | Lines lying in the same plane that are always the same distance apart. |

Parallelogram | A quadrilateral with both pairs of opposite sides parallel. Opposite angles are congruent. |

Pentagon | A polygon with five sides. |

Perimeter | The distance around a figure. |

Perpendicular | At right angles. |

Plane | A flat surface extending infinitely in all directions. |

Point | The smallest geometric unit. A position in space, often represented by a dot. |

Polygon | A simple, closed, plane figure bounded by straight sides. |

Quadrilateral | A polygon with four sides. |

Ray | A set of points that form a straight path extending infinitely in one direction. A ray has one endpoint. |

Rectangle | A parallelogram with four right angles. Opposite sides are congruent and parallel. |

Reflection | A transformation of a geometric figure that results in a mirror image of the original. |

Regular Polygon | A polygon that has equal sides and equal angles. |

Rhombus | A parallelogram with four congruent sides. Opposite angles are congruent. |

Right Angle | An angle that is one-fourth of a full turn. A right angle measures 90 degrees. |

Right Triangle | A triangle that has one right angle. |

Scalene Triangle | A triangle with no sides congruent. |

Similar Figures | that have the same shape but not necessarily the same size. |

Slide | another word for TRANSLATION |

Sphere | A three-dimensional figure formed by a set of points that are all the same distance from a fixed point called the center. |

Square | A rectangle with congruent sides. |

Symmetry | If a figure can be folded along a line so that the two halves match exactly, then the figure has line symmetry. |

Three-Dimensional | Relating to objects that have length, width, and depth. Solid figures such as polyhedra, cones, and spheres are three-dimensional. |

Translation | A transformation in which a geometric figure is formed by moving every point on a figure the same distance in the same direction. |

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

Triangle | A polygon with three sides. |

Triangular Prism | A prism in which the bases are triangles. |

Two-Dimensional | Relating to figures that have length and width but not depth. Figures such as polygons and circles are two-dimensional. |

Vertex | A point at which two line segments, lines, or rays meet to form an angle. |

Created by:
lit123
on 2010-03-18