an·​nu·​lus ˈan-yə-ləs How to pronounce annulus (audio)
plural annuli ˈan-yə-ˌlī How to pronounce annulus (audio)
also annuluses
: ring
: a part, structure, or marking resembling a ring: such as
: a line of cells around a fern sporangium that ruptures the sporangium by contracting
: a growth ring (as on the scale of a fish) that is used in estimating age

Examples of annulus in a Sentence

Recent Examples on the Web This results in the sun appearing as a bright ring, or annulus, around the dark silhouette of the moon, according to NASA. The Arizona Republic, 8 Mar. 2024 On Saturday, the moon will pass in front of the sun, obscuring much of it but leaving behind a brilliant ring, or annulus, of unfiltered sunlight in parts of the western United States. Matthew Cappucci The Washington Post, Arkansas Online, 9 Oct. 2023 Meanwhile, Matson’s boasts an extremely high level of accuracy in its cementum annuli analysis work. Katie Hill, Outdoor Life, 28 Sep. 2023 These engagement rings — known as annuli pronubi — may have changed over time, from the simple iron rings described by Pliny to those made of silver and gold. Sean Mowbray, Discover Magazine, 6 Apr. 2023 Under a low power microscope, a scale with four annuli rings would indicate a four-year period of growth, or a 4-year-old fish. Jim Gronaw, Baltimore Sun, 19 Mar. 2023 The disk is actually an annulus, like a DVD with a hole in the middle. Discover Magazine, 11 Dec. 2011 But at the playa edge, called the annulus, water continues to flow into the aquifer even after the cracks at the bottom seal up. John Richard Saylor, Discover Magazine, 18 Apr. 2021 The annulus is white, large, flaring, persistent, and is located at the top of the stalk, cup-like sheath (volva) at the base of the stalk, and white. Fox19, The Enquirer, 23 Sep. 2022

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'annulus.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History


Medieval Latin, from Latin anulus finger ring, from anus ring — more at anus

First Known Use

1563, in the meaning defined at sense 1

Time Traveler
The first known use of annulus was in 1563

Dictionary Entries Near annulus

Cite this Entry

“Annulus.” Dictionary, Merriam-Webster, Accessed 19 May. 2024.

Medical Definition


an·​nu·​lus ˈan-yə-ləs How to pronounce annulus (audio)
variants also anulus
plural annuli -ˌlī How to pronounce annulus (audio) also annuluses
: a ringlike part, structure, or marking
especially : any of various ringlike anatomical parts (as the inguinal ring)
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