To swap means to trade or exchange one thing for another. When you swap lunches with your friend, you give them your sandwich and they give you their pizza. When baseball players swap teams, each team trades players it's willing to give up for players it wants to add.

The word carries a sense of direct, straightforward exchange: I give you this, you give me that, and we both walk away with something different from what we started with. Kids often swap trading cards, books they've finished reading, or seats on the bus. Countries swap prisoners. Basketball teams swap draft picks.

A swap can also be the exchange itself: “Let's make a swap” means “Let's trade.” Sometimes people discover after a swap that they got the better end of the deal, and sometimes they realize they gave up something more valuable than what they received. The fairness of a swap depends on what both people think their items are worth.

The word swap usually suggests something casual and voluntary, not a formal business transaction. You wouldn't say a store swaps groceries for your money; you'd say you buy them. But you might swap chores with your sister, taking out the trash while she loads the dishwasher.