When something is known, it means people are aware of it or have information about it. A fact is known if people understand it to be true. A person can be known for their talents, achievements, or characteristics.

Scientists study what's already known about a topic before trying to discover something new. A math problem might ask you to find an unknown number using the known values. When detectives investigate a mystery, they start with the known facts and try to figure out what's still hidden.

The word also describes recognition or fame. A well-known author is someone many people have heard of, while a lesser-known artist might be talented but not as famous. Your neighborhood might have a known shortcut that locals use but visitors don't.

People sometimes say “it's a known fact” to emphasize that something has been proven or widely accepted. If you've known your best friend since kindergarten, you've been acquainted with them for years. The phrase “I should have known” expresses regret about missing something obvious.

Notice how known often pairs with other words to create useful expressions: a known quantity is something predictable and understood, and the known world is all the places people have explored and mapped.