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Line
A line is the path of one point moving. A line has length but no width. A line is a type of geometric figure.
A line is made up of an endless number of points.
Contents
Line segments
A line segment is part of a line. Here is an example of a straight line segment:
Straight and curved lines
A line can be straight or curved. The word line usually means a straight line. A straight line is the shortest distance between two points. A straight line is the line traced by a point moving in a direction that does not change.
A curved line is sometimes called a curve. The edge of a circle is not straight and is an example of a curve.
Naming lines
Lines can get their names from any two points on the line. For example, if a line contains two distinct points, named [math]A[/math] and [math]B[/math], then the line can be called either [math]\overleftrightarrow{AB}[/math], or [math]\overleftrightarrow{BA}[/math].
Sometimes, lines are also named with just one symbol. In which case, a letter such as [math]\ell[/math] might be used.^{[1]}^{[2]}^{[3]}
Two lines
Two lines can be:
 Parallel: Two lines are parallel if they are on the same plane and they never touch.
 Concurrent: Two lines are concurrent if they touch on one point.
 Coincident: Two lines are coincident if they are made of the same points.
 Perpendicular: Two lines are perpendicular if they make four right angles where they touch.
 Skew: In Euclidean space, two lines are skew if they are not parallel but they never touch.
Related pages
References
 ↑ "Compendium of Mathematical Symbols" (in enUS). 20200301. https://mathvault.ca/hub/highermath/mathsymbols/.
 ↑ Weisstein, Eric W.. "Line" (in en). https://mathworld.wolfram.com/Line.html#:~:text=A%20line%20is%20a%20straight,wiggles%22%20anywhere%20along%20its%20length..
 ↑ "An introduction to geometry (Geometry, Points, Lines, Planes and Angles)" (in en). https://www.mathplanet.com/education/geometry/points,lines,planesandangles/anintroductiontogeometry.

