A ring; a ringlike part or space.
- A ringlike figure, part, structure, or marking, such as a growth ring on the scale of a fish.
- A ring or group of thick-walled cells around the sporangia of many ferns that functions in spore release.
- The ringlike remains of a broken partial veil, found around the stipes of certain mushrooms.
- Mathematics The figure bounded by and containing the area between two concentric circles.