Line Segments and Rays
A segment has two endpoints; a ray starts at a point and goes on forever.
Key idea
A segment has two endpoints; a ray starts at a point and goes on forever.
In depth
A segment is the part of a line between two endpoints and has a measurable length. A ray starts at one point and goes on forever in one direction. The notation shows the difference: AB for a segment, a ray with an arrow from A through B.
Worked example
If A is at 2 and B at 7 on a number line, segment AB has length 5. Ray AB runs from 2 through 7 and beyond.
Real-world uses
- Measuring a wall length
- A laser pointer or a torch beam as a ray
Common mistake
Naming a ray with the endpoints reversed. Ray AB and ray BA point in opposite directions.
How to learn this
- Read the key idea and say it in your own words.
- Work through the worked example, then try a similar problem.
- Use the interactive lesson’s visual and mini-quiz to check the pattern.
Frequently asked questions
What is Line Segments and Rays?
A segment has two endpoints; a ray starts at a point and goes on forever. It is a topic at the beginner level in Geometry.
Where is Line Segments and Rays used in real life?
Real-world examples: Measuring a wall length; A laser pointer or a torch beam as a ray.
What should I learn before Line Segments and Rays?
Make sure you are comfortable with Points, Lines and Planes, the previous topic in Geometry.
What is a common mistake with Line Segments and Rays?
Naming a ray with the endpoints reversed. Ray AB and ray BA point in opposite directions.
How can I practise Line Segments and Rays?
Open the interactive lesson, play with the visual, then answer the three-question mini-quiz. Getting two right marks the topic complete.
What comes after Line Segments and Rays?
Move on to Angles next.
Related beginner topics in Geometry
- Points, Lines and Planes – The undefined building blocks of geometry.
- Angles – Two rays sharing an endpoint; measured in degrees.
- Types of Angles – Acute <90°, right 90°, obtuse between 90° and 180°, straight 180°.
- Measuring Angles with a Protractor – Align the baseline and read the scale.
- Complementary and Supplementary – Pairs summing to 90° or 180°.
- Triangles: Classification – By sides (equilateral, isosceles, scalene) and by angles.