an·​nu·​lus | \ ˈan-yə-ləs How to pronounce annulus (audio) \
plural annuli\ ˈan-​yə-​ˌlī How to pronounce annulus (audio) , -​(ˌ)lē \ also annuluses

Definition of annulus

1 : ring
2 : a part, structure, or marking resembling a ring: such as
a : a line of cells around a fern sporangium that ruptures the sporangium by contracting
b : 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 The spores sit inside a sturdy hoop of 12-14 cells that is called the annulus. Helen Czerski, WSJ, 25 June 2021 That force comes from the last bits of water inside the annulus cells. Helen Czerski, WSJ, 25 June 2021 That means instead of a total eclipse of the sun, viewers will witness an annular eclipse: the smaller shadow of the moon will blot out less of the sun, and the sun will shine in a brilliant ring of light (an annulus) around the darkness., 8 June 2021 An annulus, or dark ring, is formed each winter between the cementum formed in spring and summer growth periods. Alan Clemons, Outdoor Life, 18 Mar. 2021 They are easily identified by the red-brown cap fading to tan, white to lilac-gray gills, firm texture, and annulus (ring) around the stout stipe (stalk). Sunset, 22 Jan. 2018 Our last partial eclipse was Oct 23, 2014; the biggest one in recent memory is the May 10, 1994 annular eclipse (annular as in annulus = ring). Dawn Mitchell, Indianapolis Star, 18 Aug. 2017 Instead, for a few minutes the sun looks like a striking annulus, or ring, which is why an annular eclipse is also often called a ring of fire. Andrew Fazekas, National Geographic, 31 Aug. 2016 See More

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'annulus.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

First Known Use of annulus

1563, in the meaning defined at sense 1

History and Etymology for annulus

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

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The first known use of annulus was in 1563

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Cite this Entry

“Annulus.” Dictionary, Merriam-Webster, Accessed 24 May. 2022.

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More Definitions for annulus


an·​nu·​lus | \ ˈan-yə-ləs How to pronounce annulus (audio) \
variants: also anulus
plural annuli\ -​ˌlī How to pronounce annulus (audio) \ also annuluses

Medical Definition of annulus

: a ringlike part, structure, or marking especially : any of various ringlike anatomical parts (as the inguinal ring)


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