# Line

one-dimensional infinite geometric object

A line is the path of one point moving. A line has length but no width. A line is a type of geometric figure.

This is a line that curves

A line is made up of an endless number of points.

## 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 ${\displaystyle A}$  and ${\displaystyle B}$ , then the line can be called either ${\displaystyle {\overleftrightarrow {AB}}}$ , or ${\displaystyle {\overleftrightarrow {BA}}}$ .

Sometimes, lines are also named with just one symbol. In which case, 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. Retrieved 2020-08-16.