Inflected forms: pl. an·nu·lus·es or an·nu·li (-l) 1. A ringlike figure, part, structure, or marking, such as a growth ring on the scale of a fish. 2a. A ring or group of thick-walled cells around the sporangia of many ferns that functions in spore release. b. The ringlike remains of a broken partial veil, found around the stipes of certain mushrooms. 3.Mathematics The figure bounded by and containing the area between two concentric circles.
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nulus, ring, diminutive of 
