The word bank has several meanings:

1. A business where people keep their money safe and can borrow money when needed. When you deposit birthday money at a bank, it's stored securely in your account. Banks also lend money to people buying houses or starting businesses. The people who work there help customers, manage accounts, and make sure everyone's money is protected and properly recorded.
2. The ground along the edge of a river, stream, or lake. You might sit on a grassy bank fishing, or watch leaves float past from the riverbank. These slopes can be steep or gentle, muddy or covered in plants. In The Wind in the Willows, Mole and Rat live along the banks of the River Thames.
3. To tilt to one side while turning, like when an airplane banks left or right during flight, or when a cyclist banks by leaning into a turn. Birds naturally bank when they change direction in the air.
4. A supply stored for future use. A blood bank stores donated blood for medical emergencies. A seed bank preserves plant seeds in case certain crops become endangered. People sometimes talk about banking vacation days, meaning saving them up to use later.