A line segment is a limited part (including two endpoints) between two points on a straight line, which is different from a straight line and a ray. A line segment refers to a limited part between two points on a straight line, and refers to a continuous or discontinuous line composed of one or more different line elements, such as a real line segment or a two-point long line segment composed of "long strokes, short intervals, points and short intervals". A line segment is represented by letters A and B or lowercase letters representing its two endpoints, and sometimes these letters also represent the length of the line segment, which is recorded as line segment AB or line segment BA.

Line segment characteristics:

(1) is limited in length and can be measured.

(2) There are two endpoints.

(3) symmetry.

(4) The straight line between two points is the shortest distance between them.