A clue is a piece of information that helps you solve a mystery, answer a question, or figure something out. When detectives investigate a crime, they search for clues: fingerprints, footprints, or objects left behind that point toward the culprit. In a treasure hunt, each clue leads you closer to the prize.

Clues work by narrowing down possibilities. If your friend hides your backpack and tells you “it's somewhere cold,” that's a clue pointing you toward the refrigerator or freezer instead of the garage. When you're stuck on a crossword puzzle, the crossing words provide clues to help you guess the right answer.

The phrase not have a clue means someone is completely confused or doesn't understand something at all. If your teacher asks who left the classroom a mess and your classmate says, “I don't have a clue,” they're saying they have no idea who did it.

As a verb, clue in means to explain something to someone, helping them understand what's really going on.