A roost is the place where birds settle down to rest or sleep, usually perched on a branch, beam, or ledge. Chickens roost on wooden bars in their coop at night. Wild birds might roost in treetops, while pigeons roost on building ledges in cities. Birds often return to the same roost night after night, gathering together for warmth and safety.

The word also works as a verb: when birds roost, they're settling in for the night. You might watch sparrows roosting in a tree at dusk, fluffing their feathers and tucking in their heads.

There's a famous saying: “chickens come home to roost.” It means that your actions, especially bad ones, eventually catch up with you. If you've been copying homework all semester, those chickens come home to roost when the final exam arrives and you don't actually know the material. Another version people use is “the chickens have come home to roost,” meaning those consequences have finally arrived.