What are Lines, Line Segment, Rays, and Opposite Rays

What is a Line in Geometry?

Definition of a Line: A line doesn’t have a start or end point. It just goes on indefinitely in both the directions. The line has only one dimension: Length. A line usually has 2 points, but it can have many points.

You can either call it Line XY or Line a, a will always be written in small letter.

Points to remember About Line:

• No Start or End Point
• A Line continues indefinitely in both direction

You can draw many lines using a single point, but if there are 2 points only, you can draw just one line.

What is the Line Segment?

The Line Segment is just the part of the line that has 2 endpoints. In the example below, MN is the Line Segment for the first line and CD is the Line Segment for the second line.

So if you want to draw Line Segment MN and CD, it will look like the following:

What is a Ray in Geometry?

A ray has a start point and it continues indefinitely to one direction only. It cannot expand to both directions like Line does. Take an example of a Torch Beam. The start point is the Torch, but the endpoint is not certain and it lights everything it touches. Even if you relocate the torch, the start point will never change.

Here is another example of a Ray XY:

Points to Remember about Rays

• A Ray has a start point and continues indefinitely to one direction only.
• You will always define the first point of the ray at the beginning (just like the red spot in the above image with X beginning). The endpoint can be given somewhere close to the arrowhead, but not on the arrowhead.

A Video to Explain Line, Ray and Line Segment

What are the Opposite Rays in Geometry?

Opposite Rays are those 2 rays that start exactly from the same point but continues to the opposite direction. Take an example of the below Opposite Rays:

The start point for the Rays ZX and ZY is Z, and then they both go the opposite direction that makes 2 opposite rays: ZX and ZY.

Points to Remember about Opposite Rays

• Both Rays must Start from the same point
• Must go the opposite direction
• Must form a line

Identifying Opposite Rays (Video)