A bellows is a device that pushes air forcefully in one direction, like a mechanical lung that only breathes out. Traditional bellows look like an accordion made of leather stretched between two wooden boards. When you pull the boards apart, air rushes in. When you squeeze them together, the air shoots out through a nozzle.

Blacksmiths use bellows to blast air into their forges, making the fire burn hotter so they can shape metal. Before electric fans existed, bellows were essential tools. Church organs also use bellows to push air through their pipes, creating those powerful, echoing tones that fill cathedrals.

The word can also describe the action of breathing heavily and loudly, like an exhausted runner gasping for air after a sprint. When a bull bellows, it makes a deep, roaring sound from deep in its chest, much like the whooshing sound of air being forced through actual bellows.

You might encounter bellows in old-fashioned fireplaces, where people used handheld versions to coax dying embers back to life. Some accordions and bagpipes work on the same principle: squeeze the bellows, and air flows through reeds to make music.