A hopper is a container designed to hold material and release it gradually through an opening at the bottom, like a funnel that can control its flow. Think of how a gumball machine works: you turn the knob, and one gumball drops down through the narrow opening. That gumball sat waiting in a hopper until it was its turn to fall.

Farmers use hoppers to distribute seeds evenly across a field. The seeds pile up in the container, then fall through the bottom opening at a steady rate as the planting machine moves forward. Grain elevators, coal plants, and factories all use hoppers to move materials efficiently from one place to another. Even your printer has a paper hopper (though it's usually called a paper tray) that holds sheets and feeds them one at a time.

A hopper makes it possible to pour in a large amount of something all at once, then let it flow out slowly and steadily instead of dumping it all in a rush.