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# Unit 13

### 3D Figures

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

polygon | A closed plane figure formed by three or more segments. |

diagonal of a polygon | A segment that connects any two nonconsecutive vertices of a polygon. |

vertex of a polygon | A common endpoint of two sides of a polygon. |

Face | A flat surface of the polyhedron. |

Edge | A segment that is the intersection of two faces of the figure. |

Polyhedron | A closed three-dimensional figure formed by four or more polygons that intersect only at their edges. |

Vertex | The point that is the intersection of three or more faces of the figure. |

Base | A face of a three-dimensional figure by which the figure is measured or classified. |

Prism | A polyhedron formed by two parallel congruent polygonal bases connected by lateral faces that are parallelograms. |

Pyramid | A polyhedron formed by a polygonal base and triangular lateral faces that meet at a common vertex. |

Net | A pattern of two-dimensional figures that can be folded to make a three-dimensional figure. |

Surface Area | The total area of all faces and curved surfaces of a three dimensional figure. |

Lateral Face | A face of a prism or a pyramid that is not a base. |

Lateral Area | The sum of the areas of the lateral faces of a prism or pyramid, or the area of the lateral surface of a cylinder or cone. |

Tetrahedron | Triangular pyramid; A polyhedron formed by a polygonal base and triangular lateral faces that meet at a common vertex. |

Volume | The number of cubic units needed to fill a given space |

triangular prism | A polyhedron formed by two parallel congruent triangular bases connected by lateral faces that are parallelograms. |

cross section | A plane shape that results from cutting through a three-dimensional object. |

intersection | A point or set of points common to two or more geometric figures. |