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{{Short description|Part of a line that is bounded by two distinct end points; line with two endpoints}}
[[Image:Segment definition.svg|thumb
[[File:Fotothek df tg 0003359 Geometrie ^ Konstruktion ^ Strecke ^ Messinstrument.jpg|thumb|
▲[[Image:Segment definition.svg|thumb|250px|right|The geometric definition of a closed line segment: the [[intersection (Euclidean geometry)|intersection]] of all points at or to the right of {{mvar|A}} with all points at or to the left of {{mvar|B}}]]
▲[[File:Fotothek df tg 0003359 Geometrie ^ Konstruktion ^ Strecke ^ Messinstrument.jpg|thumb|historical image – create a line segment (1699)]]
{{General geometry}}
In [[geometry]], a '''line segment''' is a part of a [[line (mathematics)|straight line]] that is bounded by two distinct
Examples of line segments include the sides of a triangle or square. More generally, when both of the segment's end points are vertices of a [[polygon]] or [[polyhedron]], the line segment is either an [[edge (geometry)|edge]] (of that polygon or polyhedron) if they are adjacent vertices, or a [[diagonal]]. When the end points both lie on a [[curve]] (such as a [[circle]]), a line segment is called a [[chord (geometry)|chord]] (of that curve).
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==As a degenerate ellipse==
A line segment can be viewed as a [[Degenerate conic|degenerate case]] of an [[Ellipse#Line segment as a type of degenerate ellipse|ellipse]], in which the semiminor axis goes to zero, the [[Focus (geometry)|foci]] go to the endpoints, and the eccentricity goes to one. A standard definition of an ellipse is the set of points for which the sum of a point's distances to two
==In other geometric shapes==
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{{see also|Relative position}}
When a line segment is given an [[orientation (vector space)|orientation]] ([[direction (geometry)|direction]]) it is called a '''directed line segment''' or '''oriented line segment'''. It suggests a [[translation (geometry)|translation]] or [[displacement (geometry)|displacement]] (perhaps caused by a [[force]]). The magnitude and direction are indicative of a potential change. Extending a directed line segment semi-infinitely produces a ''[[
==Generalizations==
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An [[oriented plane segment]] or ''[[bivector]]'' generalizes the directed line segment.
Beyond Euclidean geometry, [[geodesic segment]]s play the role of line segments.
A line segment is a one-dimensional ''[[simplex]]''; a two-dimensional simplex is a triangle.
==Types of line segments==
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==External links==
{{commons
{{Wiktionary|line segment}}
*{{mathworld |urlname=LineSegment |title=Line segment }}
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