annulus

/ˈænjʊləs/

//ˈænjʊləs// noun

By · According to Wiktionary data (CC BY-SA) ·

"annulus" is a 7-letter English headword indexed on PlainSpell.

The verdict

“annulus” is uncommon English (frequency #69,641 among 3,931 “A” headwords), classed as a noun. The kind of spelling people second-guess.

#69,641
frequency rank, English
3,931
“A” headwords

According to Wiktionary data (CC BY-SA, analyzed September 3, 2026) - A ring- or donut-shaped area, object, or structure.

Corpus desk

Index EN-annulus · annulus · English

annulus · rank #69,641 · 0 variants · 0 confusables

  • FREQ-RARE #69,641
  • LEN-LONG 7 letters
  • VOW-3 3 vowels
  • CONFUS-0 No pairs
  • VAR-0 0 variants
  • BOOK-MID 3,931
  • PHOTO-FINISH anhydride

Nearest frequency peer: anhydride (-1 rank slots)

Read with this headword: Spelling guide for this pattern

Desk codes from Wiktionary headword shape, FrequencyWords rank tier, confusable-pair count, generated misspelling depth, letter-cohort book size, and photo-finish peer. Not a difficulty grade.

Long-tail ranks near “annulus”

Sparse band: bars invert rank so rarer forms read shorter

corpus weight

What this shows Long-tail view: where “annulus” sits against similarly uncommon English ranks.

Source FrequencyWords open word-frequency list As of September 3, 2026
Key facts for annulus
PropertyValue
Headwordannulus
LanguageEnglish
Part of speechNoun
IPA/ˈænjʊləs/
Letters7
Frequency rank#69,641
Misspellings tracked0
Confusable pairs0
SourceWiktionary (kaikki.org)

Long-tail rank of “annulus” in English

Word frequency stretches from the small set of words we reach for constantly (left) out to the long tail barely used once in a while (right).annulusfalls in this rarity band:

#1#100#1K#10K#100K
← used constantlyrarely used →

Ticks step logarithmically, so each one marks a roughly tenfold drop in how often the word turns up. Rare peers in the same band: “anhydride” (#69,640), “Antibes” (#69,642), “andesite” (#69,639). Among 3,931 “A” headwords, “annulus” is #69,641. Source: FrequencyWords open word-frequency list.

Rare enough to double-check

annulus is uncommon English at frequency #69,641 among 3,931 “A” headwords, classed as anoun, transcribed /ˈænjʊləs/. Rarity is why readers land here mid-draft. 9 senses are on record.

No misspelling variants are generated for annulus in our index, since its letter pattern doesn't lend itself to common typo substitutions. No confusable counterpart is on file for this word, a sign it's visually distinctive enough not to be mixed up with another word.

Etymologically, the entry records: Learned borrowing from Medieval Latin ānnulus, a misspelling of Latin ānulus (“ring, especially one worn on a finger”), from ānus (“ring”) (possibly from Proto-Indo-European *h₁eh₂-n-o- (“ring”), from an uncertain root) + -ulus (diminutive suffix). The plur… The correct English form is annulus, spelled A-N-N-U-L-U-S.

Definition

  1. 1
    A ring- or donut-shaped area, object, or structure.
  2. 2
    A ring of fibrous tissue; specifically (cardiology), such a ring around an opening of a heart valve, to which the valve leaflets and muscle fibres of the atria and ventricles are attached; an annulus fibrosus cordis.
  3. 3
    A ring of light in a celestial body, especially when caused by an annular eclipse (for example, when the Sun and Moon are in line with the Earth, but the Moon does not completely cover the Sun's disc).
  4. 4
    A structure surrounding a sporangium (or part of it) which shrinks and causes it to rupture for spore dispersal; specifically, in a fern: a structure around about two-thirds of the sporangium consisting of differentially thick-walled cells which dry and distort the sporangium; and in a moss: a complete ring of cells around the tip of the sporangium which dissolves to cause the tip to detach.
  5. 5
    The membranous remnants of a partial veil which leaves a ring on the stem of a mushroom.
  6. 6
    A dark ring on a fish's scale that is formed when a fish's growth rate slows down in the winter due to low food intake and the scale's circuli move closer to one another. The dark ring is used to estimate the fish's age, approximately one year per annulus.
  7. 7
    The region in a plane between two concentric circles of different radii.
  8. 8
    Any topological space homeomorphic to the region in a plane between two concentric circles of different radii.
  9. 9
    In a well such as an oil well or water well: the space between a pipe or tube and any pipe, tube, casing, or sides of a hole surrounding it.

Recorded use

Wiktionary examples

These source excerpts show how annulus appears in context. They illustrate usage; the definition above remains the entry’s reference meaning.

  1. But by the knots I am ſpeaking of, may it pleaſe your reverences to believe, that I mean good, honeſt, deviliſh tight, hard knots, made bona fide, as Obadiah made his;—in vvhich there is no quibbling proviſion made by the duplication and return of the tvvo ends of the ſtrings through the annulus or nooſe made by the ſecond implication of them— […]
  2. Pressure balance is obtained by the air pressure in the cylinder operating on a supplementary piston in the buffer piston head, transmitting pressure to a small quantity of oil which is ported to an annulus between the buffer piston seals and the cylinder wall, so that the seal is always under opposing pressures; oil on one side and air on the other.

Etymology

Learned borrowing from Medieval Latin ānnulus, a misspelling of Latin ānulus (“ring, especially one worn on a finger”), from ānus (“ring”) (possibly from Proto-Indo-European *h₁eh₂-n-o- (“ring”), from an uncertain root) + -ulus (diminutive suffix). The plural form annuli is a learned borrowing from Medieval Latin ānnulī.

This word in other languages

anillo(Español)anneau(Français)Ring(Deutsch)anel(Português)

Definitions, pronunciation, and etymology for this entry are drawn from Wiktionary via the kaikki.org structured extract (CC BY-SA); frequency ordering uses the FrequencyWords open word-frequency list (2018 English corpus, MIT). See the methodology for how each field is sourced and updated.

Frequently Asked Questions

How do you spell "annulus"?
"annulus" is spelled A-N-N-U-L-U-S. The IPA pronunciation is /ˈænjʊləs/.
What does "annulus" mean?
As a noun, "annulus" means: A ring- or donut-shaped area, object, or structure.
How do you pronounce "annulus"?
The IPA (International Phonetic Alphabet) transcription for "annulus" is /ˈænjʊləs/. Click the speaker icon on the pronunciation badge above to hear it spoken aloud where audio is available.
What is the origin of the word "annulus"?
Learned borrowing from Medieval Latin ānnulus, a misspelling of Latin ānulus (“ring, especially one worn on a finger”), from ānus (“ring”) (possibly from Proto-Indo-European *h₁eh₂-n-o- (“ring”), from an uncertain root) + -ulus (diminutive suffix)... See the full etymology section above for more details.
Is PlainSpell free to use?
Yes, PlainSpell is a completely free word reference. You can look up definitions, pronunciations, confusable pairs, homophones, and spelling corrections across 5 languages without any sign-up or subscription.

Similar English words by spelling shape

Same letter count and similar misspelling depth for "annulus", not the corpus desk frequency band.

Same letter count

Frequency-ranked English headwords with 7 letters (nearest by frequency rank).

Antibes#69,642Alessia#69,631axially#69,656Ackroyd#69,621

Source: Wiktionary (via kaikki.org) Structured Wiktionary extract

Source: FrequencyWords open word-frequency list