A line segment is a part of a line that connects two distinct endpoints. Unlike a line, which extends infinitely in both directions, a line segment has a definite start and end point, giving it a fixed length that can be measured. It is essentially a piece or section of a line bounded by these two endpoints. The length of a line segment is the shortest distance between its endpoints. In geometry, a line segment is often represented by a bar above the symbols representing its endpoints. For example, a line segment with endpoints P and Q is denoted as PQ‾\overline{PQ}PQ​. Unlike a ray, which has one endpoint and extends indefinitely in the other direction, a line segment has two endpoints and does not extend beyond them. Examples of line segments include the sides of polygons such as triangles and squares. In summary:

• A line segment has two endpoints.
• It has a definite length.
• It is a part of a line, not infinite like a line itself.
• It can be measured directly.

This makes line segments fundamental geometric objects used in various mathematical contexts.