Ray
In short
A ray is a part of a line that starts at a single point and goes on forever in one direction.
In plain words
Imagine a starting dot on a piece of paper. From that dot, you draw a straight line that never ends. It has a beginning but no end.
A simple example
A beam of light from a torch is like a ray. It starts at the bulb and travels straight out into the dark.
Why it matters
Rays are essential in geometry to define angles and describe how light moves. They help scientists map out paths of energy and particles.
Easy to mix up
Do not confuse a ray with a line segment, which has two fixed endpoints and does not go on forever.