A spy is someone who secretly gathers information about an enemy or competitor. Spies work in the shadows, watching, listening, and reporting back what they learn without being discovered. During World War II, spies helped the Allies by learning about enemy troop movements and secret weapons. Today, government intelligence agencies employ spies to protect national security by discovering what other countries or terrorist groups are planning.

Spying requires exceptional skills: memorizing details quickly, noticing things others miss, and staying calm under pressure. A spy might need to speak multiple languages, blend into different cultures, or create convincing false identities. The work is dangerous because getting caught can mean imprisonment or worse.

The word also describes everyday noticing. When you spy your friend hiding something behind their back, you've spotted them secretly. Kids might spy on their older siblings to learn what they're planning. A detective novel might feature characters spying through keyholes or eavesdropping on suspicious conversations.

A spy can also be someone who secretly watches or investigates for any organization, not just governments. Companies sometimes accuse competitors of sending spies to steal business secrets or new product designs.