The definition of line segment in the second grade of primary school: refers to a continuous or discontinuous line composed of one or more different line elements, which is a limited part between two points on a straight line. Features: limited length, measurable; There are two endpoints; There is symmetry; The straight line between two points is the shortest distance between them.

First, in the application of life, there are three main types of line segments-linking, separating and deleting:

The 1. link binds the two in different places, as do other indicative supplements.

2. Separation separates two areas in the same place, as do other areas such as depth of field and equipotential line.

3. Delete examples: When writing an article, in order to keep the creative process, cross out inappropriate sentences with lines, as do other stops in the route.

Second, the theory of line segment formation:

A line segment consists of countless points. If there is no space between points, then points cannot be said to have length, that is, they are all isolated, and the length of line segments cannot be obtained. To be correct, there are infinitely many points, and the length of the line segment has nothing to do with the length of the point. Two values with different scales cannot be simply extrapolated directly. Finite and infinite cases cannot be simply extrapolated.

There is also a saying that is explained from the viewpoint of motion: a line segment is the locus of a point. But in real life, people have long acquiesced in the saying that "line segments are composed of countless points".