A reflector is something that bounces light, sound, or heat back instead of absorbing it. The most familiar reflectors are mirrors, which reflect light so clearly that you can see your own face looking back at you. But many things act as reflectors: a white shirt reflects sunlight and keeps you cooler than a black one, while a shiny bicycle reflector bounces car headlights back to drivers so they can see you in the dark.

Reflectors work because different surfaces interact with energy in different ways. Smooth, shiny surfaces make the best reflectors for light. That's why telescopes use curved mirrors as reflectors to gather and focus light from distant stars. Sound reflectors work similarly: when you shout in a canyon and hear an echo, the rock walls are acting as reflectors, bouncing your voice back to you.

The word can also describe a person who thinks carefully about things, but in this sense, people are usually called reflective rather than reflectors.