*Kiddle Encyclopedia.*

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.

## 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 has a point named "*A*" on the line and a point named "*B*" on the line, then the line can be called either "*AB*" or "*BA*".

Sometimes, lines are also named with just one letter; for example, line *A*.

## 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: Two lines are skew if they are not parallel but they never touch.