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Homelength

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# 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.

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, it is customary to refer to the length of any of its sides as the *length of the polygon*. 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 $5$.

## Mathematics Subject Classification

51D20*no label found*51-00

*no label found*51M25

*no label found*

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