A ring is a circular or oval shape, like the rings around Saturn or a ring of trees surrounding an open field, or the ring of delicious fried pastry that we call a doughnut.
Angels are often shown in paintings with a ring hovering over their heads — a halo. And if you've ever ordered onion rings, you know that they're circle-shaped slices of onion that are battered, fried, and eaten with ketchup. Then there's the ring, usually made of silver or gold, that's worn as jewelry on a finger. As a verb, to ring is to form a circle, as in the children's song and game "Ring Around the Rosie."