# length

The *length* of a line segment^{} is the distance between its endpoints. Length may be measured in meters, yards, abstract units, etc. For example, in the following diagram

$AB$ is one unit long, $BC$ is two units long, $CD$ is a fifth of a unit, $DE$ is four fifths of a unit, $AC$ is three units, etc.

The concept of length as defined above is a special case of a general concept called measure.

In two-dimensional space, length usually goes along the $x$ axis while height goes along the $y$ axis. The same holds in three-dimensional space.

For triangles^{}, pentagons^{}, and higher $n$-gons (http://planetmath.org/BasicPolygon), it is customary to refer to the length of any of its sides as the *length of the *. The length of a circle’s side is called its circumference^{}.

In set theory^{}, *length* refers to the number of elements a set (or one-dimensional array) has. This is also known as cardinality. For example, $\{2,5,11,23,47\}$ has length $5$.

Title | length |

Canonical name | Length |

Date of creation | 2013-03-22 16:31:45 |

Last modified on | 2013-03-22 16:31:45 |

Owner | PrimeFan (13766) |

Last modified by | PrimeFan (13766) |

Numerical id | 17 |

Author | PrimeFan (13766) |

Entry type | Definition |

Classification | msc 51D20 |

Classification | msc 51-00 |

Classification | msc 51M25 |

Related topic | Area2 |

Related topic | Volume2 |

Related topic | BasicPolygon |

Defines | length of a polygon^{} |

Defines | length of a set |