Find the "points" at the end of the line segment you wish to identify. A line segment always falls between two points. Even if it crosses a third point in between, these "bounds" are always the ones that will define or "name" the line.
Write the names of the points next to one another. In abstract space, points are given letter names; therefore, write AB, or whichever letters correspond to the points. If you are working on a number line, or a Cartesian plane, skip to Step 4.
Draw a short, straight line over the letters to denote a line "segment." This will be read, "the line segment bounded by point A and point B," or simply, "segment A-B." You have identified this segment, and you do not need the following steps.
Check to see whether the line includes the points. If your line segment falls on a number line or Cartesian plane, its distance can be measured in discrete units. Some lines include the points they are bounded by, which is indicated by a darkened circle at the point in question, while others exclude them, which is indicated by an open circle.
Identify these segments by the coordinates of the points that bound them. If a line goes from -2 to 2, inclusive, on a number line, then the coordinates are -2 and 2. On a Cartesian plane, the coordinates have two parts: horizontal and vertical. These points may be written "(-2, 2)" and "(2, 3)."
Identify the segment using "greater than" and "less than" signs. If the line segment lies between -2 and 2, exclusive, you can write "-2 < 2." To indicate that the segment is inclusive, you must use a "greater than or equal to" sign, by drawing a line under the "<." If one end (-2) is included and not the other (2), the simplest way to identify the line segment is _> -2 and < 2.