A fractal is a geometric pattern that repeats itself at different scales, where each small part looks similar to the whole thing. If you zoom in on a fractal, you'll see the same basic pattern appearing again and again, no matter how close you look.

Nature creates fractals everywhere. A fern leaf shows this beautifully: the whole leaf has a particular shape, but each small branch off the main stem looks like a tiny version of the entire leaf, and each tinier branch looks like an even smaller version. Broccoli works the same way: each floret looks like a miniature head of broccoli. Coastlines, snowflakes, lightning bolts, and tree branches all display fractal patterns.

Fractals fascinate mathematicians and artists alike because they reveal a hidden order in things that look chaotic or random. Computer programs can generate stunning fractal images with endlessly repeating patterns, and scientists use fractals to model everything from cloud formations to how blood vessels branch through your body. The key insight is that complex, beautiful patterns can emerge from simple rules that repeat at every level.

As an adjective, fractal describes something that has this kind of repeating, self-similar structure.