Lines, Rays & Line Segments

Today's big idea

Only the ends tell a line, a ray and a line segment apart, never the length.

Dots stop the figure; arrows send it on forever.

How it works

👀 What's going on?

A pencil has two ends, and you can touch them both. A beam from a torch has one end at the bulb, and the other end is far out in the dark.

💡 Here's the trick

Look at the three figures above. All three are straight, so only the ends tell them apart. A dot means the figure stops there, and that dot is called an endpoint. An arrow means it carries on forever. Two dots make a line segment, one dot and one arrow make a ray, and two arrows make a line.

🪄 How to do it

1.Look at one end of the figure above and see whether it is a dot or an arrow.
2.Check the other end in exactly the same way.
3.Two dots is a segment, one dot and one arrow is a ray, two arrows is a line.

✍️ Try it

1.A torch beam starts at the bulb and shines away as far as it can go. Which of the three names fits it?
2.Sana draws a line segment. She rubs out both of its dots and draws an arrow at each end instead. What has her figure become?

1.The beam starts somewhere and never stops, so it has 1 endpoint and 1 arrow. That makes it a ray.
2.Her figure now has no dots and 2 arrows. Two arrows means it runs on forever both ways, so it has become a line.

⚠️ Watch out

You might be thinking that a line segment is just a short one and a line is a long one. Length has nothing to do with it. A segment drawn right across a whole wall is still a segment, because it has a dot at each end. A tiny figure with arrows on both ends is still a line.

🌟 Why this matters

A fence panel runs between two posts and stops, so it works like a segment. A torch beam leaves the bulb and keeps going, so it works like a ray. Using the right word tells someone straight away where a thing starts and where it stops.
Exam tip: SilverZone Class 3 papers nearly always include one name-this-figure question.

Watch me solve one

Quanta solves it

“Watch how I think through one of these — then you try.”

THE PROBLEM

“A straight figure has a dot at one end and an arrow at the other. What is it called?”

1
Check both ends
One end = dot (a stop). Other end = arrow.
2
What each end means
A dot stops the figure; an arrow means it goes on forever that way.
3
Match to the rule
Starts at a point, goes on one way → RAY.
4
Answer ✓
= Ray

Now you try one — same steps, different story 👇

See it in action

⚡ Time to play!

Look at the dots and arrows, then tap what this figure is.

LINES · ROUND 1 OF 3

Quick check

✅ VERIFICATION

Which one of these can you measure with a ruler and give an exact length?

⚡ Finish the activity above first to answer.

Keep going!

Up next: 2D Shapes

Count the sides, 3 = triangle, 4 = quad, 5 = pentagon.

Concept 3 of 7 →