annulus

noun

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
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
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
Key Facts Parts of the world will witness a ring of fire annular solar eclipse Wednesday, in which the moon passes between the sun and Earth but does not completely obscure the sun, leaving the sun’s visible outer edge—also called the ring of fire, or annulus—around the moon. — Arianna Johnson, Forbes, 2 Oct. 2024 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

Word History

Etymology

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

Browse Nearby Words

Annulosa
annulus
annunciate
See all Nearby Words

Cite this Entry

“Annulus.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/annulus. Accessed 4 Apr. 2025.

Copy Citation

Share

Medical Definition

annulus

noun
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)
Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!

Popular in Grammar & Usage

See More

How to Use Em Dashes (—), En Dashes (–) , and Hyphens (-)

The Difference Between 'i.e.' and 'e.g.'

Why is '-ed' sometimes pronounced at the end of a word?

Words You Always Have to Look Up

Democracy or Republic: What's the difference?
See More

Popular in Wordplay

See More

What do SCOTUS, POTUS, and FLOTUS mean?

Top 10 Sophisticated Insults

More Words with Remarkable Origins

Terroir, Oenophile, & Magnum: Ten Words About Wine

8 Words for Lesser-Known Musical Instruments
See More

Popular

See More

How to Use Em Dashes (—), En Dashes (–) , and Hyphens (-)

What do SCOTUS, POTUS, and FLOTUS mean?

Top 10 Sophisticated Insults
See More

Games & Quizzes

See All
Play Quordle: Guess all four words in a limited number of tries. Each of your guesses must be a real 5-letter word.
Quordle Can you solve 4 words at once?
Play Blossom: Solve today's spelling word game by finding as many words as you can using just 7 letters. Longer words score more points.
Blossom Word Game Pick the best words!
Play Missing Letter: a crossword with a twist. Each of the 25 puzzle words start with a different letter of the alphabet. Which letter is missing?
Missing Letter A daily crossword with a twist
kestrel
Name That Bird Quiz Are you as wise as an owl or just another birdbrain?
See All