Definition of Line

A line is straight, flat, and extends infinitely in two directions. Through any two points, there is one and only one line that can be drawn . Two lines either intersect in one point or they are parallel and never intersect. The term straight line is also used to refer to a line.

Definition of Segment

A segment is a finite portion of a line and is determined by its two endpoints. A segment consists of its two endpoints together with all the points that are between the endpoints and on the line connecting them. The length of a segment is a measure of its size and is the same as the distance between its two endpoints. The terms line segment and straight line segment are also used to refer to a segment.

Definition of Ray

A ray is half of a line and goes on infinitely in one direction. It is determined by its endpoint and another point that shows which half of the line constitutes the ray. A ray consists of its endpoint and all points on that half of the line.

In the sketch below, you see a line, a segment, and a ray. Drag any of the red points to change the direction or position of the straight objects. The length of the segment can be changed by dragging either of its endpoints.

Sorry, this page requires a Java-compatible web browser.

Back to Overview of Lines

References and Credits