Line Segment and Ray

To learn about lines, line segment and ray, we will first have to know what is point and line. A point is the most basic structure of geometry. All the shapes are made when they are combined through points. A point is a small dot marked by a pencil. It has no length or width. It also has no thickness. It is the mark of the position. It specifies the exact location a structure must be constructed. It is denoted by a dot (.) and named by any alphabet. Now we look at a line. 

What is a Line?

A line can stretch on both the end without any end. The ends of the line can go to infinity. It has no endpoints and no definite length unless it is structured by marking the two points. It is named by any two points on it, which is described as line AB or line PQ. Only a single line can be drawn between two points. A horizontal line goes left to right, and the vertical line goes up and down.

In our day-to-day life, we come across various shapes, for instance, a triangle, square, or any other shape as such. To structure these figures, we begin with a line segment or a curve. Depending on the arrangement and the number of lines, we get various types of shapes and figures. For instance, a square is a figure of 4-line segments; a pentagon has five-line segments. Now let us further learn about line segment and ray.

What is a Line Segment?

A line segment is a type of line that begins from one point and ends at another point. In other words, a section of a line is a line segment. A line segment has two endpoints with a straight line that connects the two points. A line segment has a certain length, and it can be measured. Only one line segment can be given two points.

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In the above figure, a line segment PQ has two endpoints that are P and Q. It starts from point P and ends at point Q. it is called line segment PQ or line segment QP. Line segments can also be part of a line, or it may also be a part of the ray. 

Four Types of Line Segment

  1. Parallel Line

Two lines in the same plane either meeting each other or not. When two lines on the same plane do not meet each other at any point, it is known as a parallel line.

  1. Intersecting Lines

Intersecting lines are two or more lines crossing each other in a plane. They share a common point that exists on all the intersecting lines and is called the point of intersection.


  1. Concurrent Lines

When multiple lines pass through each other at the same given point is known as parallel lines. 


  1. Collinear Points

When there are three or more points on a single line, it is known as collinear points.

What is a Ray?

When we talk about ray, the first thing that comes to our mind is a torch. The light emits from it and moves away. We can also take the example of the sun. The rays of the sun start from it and can go in all the directions. 

Similarly, in Geometry, a ray starts from a point and may go up to infinity. It has a start point but no endpoint. In other words, we say that a ray has one point and goes without end in one direction. The length of the ray cannot be measured. From a given point, we can draw an unlimited number of rays in different directions.

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Difference Between Line-Segment and Ray

  1. Endpoints

A line segment has two endpoints.


A ray has one start point but no endpoint. 


  1. Length

A line segment has a definite length; therefore, it is measurable.

A ray has a start point but no endpoint; therefore, it cannot be measured.


  1. Symbol

The symbol of a line segment is (_______).

The symbol of a ray is ().

In geometry, a line segment is written using letters for each of the endpoints. If your endpoints are A and B, you would then write it as line segment AB. For a ray on the other hand, it starts at one point and goes on indefinitely in one single direction. This is also represented by AB but has a -> sign on its head (line and arrowhead). A line segment is written as AB with a line on its head (no arrow heads at either ends).

FAQ (Frequently Asked Questions)

1. What is a Line, Line Segment and Ray?

A line is an infinite line with no starting and endpoint. It can stretch in both directions up to infinity. A line cannot be measured. A line segment is a definite line having two points, a start point, and an endpoint. It can be measured as it is decisive. A ray has a start point but no endpoint; it is like the light of a torch or a sun that originates from a point but does not end anywhere. It can go into multiple directions with only one starting point in another direction.

2. Does a Line Segment go on Forever?

A line is extensive, like a point having an infinite number of points (in a straight row). It can extend forever in both directions. Two lines can only intersect at one single point. We can get a line segment on a line when two points, i.e., start and endpoints, are marked. On the other hand, a ray is a geometrical figure that has a start source but has no end. However, a line segment has a fixed length, it has both the source and the end. Hence, a ray cannot be a part of the line segment, but a line segment can be a part of the ray.