A fact or situation that is observed to exist or happen, especially one whose cause or explanation is in question. The Northern Lights are a natural phenomenon that attracts tourists from all over the world.
A remarkable person, thing, or event. The young chess player was considered a phenomenon for his extraordinary skills at such a young age.
In philosophy, an object of sensory experience as distinguished from a thing as it is in itself (noumenon). Kant argued that we can have knowledge only of phenomena, never of things-in-themselves.