Minecraft wiki entry for Villager, associated text: The trading system is a gameplay mechanic that allows players to buy and sell various items to and from villagers, using emeralds as a currency. Their trades can be valuable or somewhat meaningless, depending on the cost, the items the player might get, and how the player treats the villagers. Only adult villagers with professions can trade; the player cannot trade with nitwits, unemployed villagers, or baby villagers. Attempting to do so causes the villager to display a head-shaking animation and play the villager's declined trade sound‌[Java Edition only].