Unknown means not known, not familiar, or not identified. When something is unknown, you don't have information about it yet. A math problem with an unknown variable (often represented by x) is asking you to figure out what number belongs in that spot. When explorers set out into unknown territory, they're traveling to places no one in their group has mapped or studied before.

The word can describe people too. An unknown actor is someone the public hasn't heard of yet, even if they're talented. Many famous musicians and athletes started as unknowns before their hard work and skill brought them recognition. Being unknown doesn't mean being unimportant; it just means not yet discovered or identified.

Scientists love unknowns because they represent unsolved mysteries waiting to be figured out. Every major discovery in history started as an unknown, something people didn't understand until someone investigated it carefully. When a detective solves a case, they're identifying the unknown culprit. When you research a topic you've never studied before, you're exploring the unknown.

Sometimes people use “unknown” as a noun, like “venturing into the unknown” or “fear of the unknown,” meaning unfamiliar situations or unexplored possibilities.