# Line

A line is the path of one point that is moving. A line is a type of geometric figure. A line has length, but no width. A line is made up of an endless number of points.

## Straight and curved lines

A line can be straight or curved. In geometry, the word line means a straight line. A straight line is the shortest distance between two points. A straight line is 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. It is an example of a curve.

## Line segments

A line segment is part of a line. Here are examples of straight line segments:

_____   __

## Naming lines

Lines can get their names from any two points on the line. For example, if a line contains two different points, named ${\displaystyle A}$ and ${\displaystyle B}$, then the line can be called either ${\displaystyle {\overleftrightarrow {AB}}}$, or ${\displaystyle {\overleftrightarrow {BA}}}$.

Sometimes, lines are named with just one symbol. A letter such as ${\displaystyle \ell }$ 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.

## References

1. "Compendium of Mathematical Symbols". Math Vault. 2020-03-01. Retrieved 2020-08-16.
2. Weisstein, Eric W. "Line". mathworld.wolfram.com. Retrieved 2020-08-16.
3. "An introduction to geometry (Geometry, Points, Lines, Planes and Angles)". Mathplanet. Archived from the original on 2020-09-29. Retrieved 2020-08-16.