A thief is someone who steals things that belong to other people. When a thief takes something, they know it isn't theirs and they know the owner doesn't want them to have it, but they take it anyway, usually in secret.

Thieves might steal small things like candy from a store or big things like bicycles, cars, or even money from banks. What makes someone a thief is the deliberate choice to take what isn't theirs. If you accidentally bring home your friend's pencil, you're not a thief. But if you see their new video game and slip it into your backpack when they're not looking, that's stealing.

Throughout history, thieves have been considered criminals in virtually every society. Laws against stealing exist because communities can't function when people can't trust each other with their belongings. A petty thief steals small, inexpensive items, while thieves who steal valuable things or use threats can face more serious consequences.