annulus

American  

[an-yuh-luhs] / ˈæn yə ləs /

noun

plural

annuli, annuluses

1. a ring; a ringlike part, band, or space.

2. Geometry. the space between two concentric circles on a plane.

3. the veil remnant on a mushroom stalk.

4. a growth ring, as on the cross section of a tree trunk, that can be used to estimate age.

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annulus British  

/ ˈænjʊləs /

noun

1. the area between two concentric circles

2. a ring-shaped part, figure, or space

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annulus Scientific  

/ ăn′yə-ləs /

plural

annuluses

1. A ringlike figure, part, structure, or marking, such as a growth ring on the scale of a fish.

2. A ring or group of specialized cells around the sporangia of many ferns. By changing shape in response to variations in humidity, it breaks open the sporangium and then releases the spores with a whipping motion.

3. The ringlike remains of a membrane (called a veil), found around the stipes of certain basidiomycete mushrooms. The presence or absence of an annulus is often used to identify the species of an individual mushroom.

4. The figure bounded by and containing the area between two concentric circles.

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Etymology

Origin of annulus

1555–65; < Latin, variant of ānulus, equivalent to ān ( us ) ring + -ulus -ule

Example Sentences

Shells have always played an important role in Mauritian culture - the Monetaria annulus, commonly known as gold ring cowrie, is a gift of love or luck.

From BBC • Dec. 28, 2021

Figure 6.45 Breaking the annulus into two separate regions gives us two simply connected regions.

From Textbooks • Mar. 30, 2016

Its tubercles and soft tissues were inflamed, and the annulus fibrosus of its disks was the color of bad teeth.

From The New Yorker • Feb. 28, 2011

Another device on the stack, a doughnutlike rubber ring called an annular preventer, can seal the annulus but still allow the drill pipe to be moved up or down.

From New York Times • May 10, 2010

The stem is equal, firm, stuffed, rough, with thick squarrose scales, white above the thick floccose annulus, pallid or tawny below.

From The Mushroom, Edible and Otherwise Its Habitat and its Time of Growth by Hard, Miron Elisha