Subject: Geometry

Line Segments

By now, you already know about basic geometry words and symbols. In the last article, we discussed about lines, points and planes. In this article, let us know more about lines. Let us study Line Segments.

The string of a guitar is an example of a
line segment.

Line Segments

Line segment is defined as a part of a line that is bounded by two end points, and contains every point on the line between its end points. It is basically a straight line which connects two points (two endpoints) without extending beyond them.

In the above figure, the line segment AB connects the red points A and B. These red points are known as the 'endpoints' of the line segment AB. Line segment is just a subset of a line which would basically reach to infinity. The word "segment" basically means 'a piece' of something, and line segment means the piece of a full line.

Properties of a line segment

Length of line segments can be measured. It has a real-valued dimension. However, length is the only attribute of a line segment. In short, line segments are one-dimensional. It has no width, mass, height or whatsoever.


There are many ways to give line segments its identity. In geometry, there are two ways to name line segments. These are as follows;

  • Naming line segments by its endpoints.

We can name line segments by the endpoints A and B as seen in the figure above. By putting a bar above the two endpoints A and B (\bar{AB}), it can now be called as "line segment AB". If there is no bar above two endpoints, say AB, then it is called line AB. But if there's a bar above two endpoints A and B, (\bar{AB}), then it is called as "line segment AB".

  • Naming line segments by a single letter.

Line segments can also be named according to letters. Any letter can be used to name line segments. In the figure above, the line segment AB can simply be called "x" or "line segment x".