A phenomenon is something remarkable or unusual that can be observed and studied. When scientists notice that fireflies all start blinking in sync, or that ice crystals form stunning patterns on a window, they're observing natural phenomena (the plural of phenomenon). The northern lights, earthquakes, and solar eclipses are all phenomena that people have watched and wondered about for thousands of years.

The word also describes anything that becomes wildly popular or captures widespread attention. When a new book series suddenly has every kid in school reading it, or when a song becomes so popular that everyone knows the lyrics, that's a cultural phenomenon. The hula hoop became a phenomenon in the 1950s, spreading across America in just months.

What makes something a phenomenon is that it's notable: it stands out enough that people pay attention and talk about it. A regular rainstorm is just weather, but a double rainbow that appears right at sunset might be called a phenomenon. A good student is admirable, but a ten-year-old who composes symphonies is a phenomenon.

Scientists use this word to describe events they want to understand better. Before people understood what caused lightning, it was simply a mysterious phenomenon. Once scientists figured out the electrical process behind it, lightning was no longer mysterious, but it's still a fascinating natural phenomenon worth studying.