A prism is a solid object, typically made of glass or clear plastic, with flat surfaces and identical ends. The most common type is a triangular prism, which looks like a long triangle stretched out into three dimensions, like a tent or a Toblerone candy bar.

Prisms are famous for splitting white light into rainbows. When sunlight passes through a glass prism, it bends and separates into many colors you might see in a rainbow: red, orange, yellow, green, blue, indigo, and violet. This happens because different colors of light bend by slightly different amounts as they pass through the glass. Isaac Newton used a prism in the 1600s to show that white light actually contains all these colors mixed together, a discovery that changed how scientists understood light.

You might see prisms used as decorations that cast rainbow patterns on walls when sunlight hits them, or in scientific instruments like binoculars and cameras. In math class, you'll learn that prism also refers to any three-dimensional shape with two identical flat ends connected by flat sides. Whether it's a rectangular prism (a box shape) or a hexagonal prism (with six-sided ends), the key idea is those matching end shapes connected by flat sides.