operculum

English

Illustration of a fish's opercular series, with the operculum (yellow), preoperculum (red), interoperculum (green) and suboperculum (pink).

Sea snail with its operculum covering the aperture.

The operculum of the brain.

Flower buds of Eucalyptus erythrocorys, with and without opercula.

Etymology

Etymology tree

Proto-Indo-European *h₁ep-der.

Proto-Indo-European *h₁épsder.

Proto-Indo-European *h₁épi

Proto-Indo-European *h₂wer-

Proto-Indo-European *-yeti

Latin operiō

Latin -culum

Latin operculumbor.

English operculum

Borrowed from Latin operculum.

Pronunciation

• (UK) IPA^(key): /əʊˈpɜː.kjʊ.ləm/
• (US) IPA^(key): /oʊˈpɝ.kjə.ləm/

• Audio (US):

  (file)

Noun

operculum (plural opercula)

1. (zoology) A covering flap in animals and insects, such as a gill cover or the lid of nits.
   • 2017 January 18, Susannah Lydon, The Guardian‎^[1], archived from the original on 18 October 2026:

     Hyoliths […] have a small, conical calcium carbonate shell, with a lid called an operculum.

   • 2023, translated in 2025, Berta Páramo and translated by Marc Correa Haro, Lice: How to Survive on Humans, page 110:

     As the egg comes out, it gets covered in glue. All it needs now is the operculum, a little lid that will help your kid breathe.

2. (botany) The lidlike portion of a moss sporangium or of a fruit that detaches to allow the dispersal of spores or seeds.
3. (dentistry) A gum flap covering (part of) a partially erupted tooth, usually a wisdom tooth.
4. A structure which serves as a cover or lid.
   • 1900 December – 1901 August, H[erbert] G[eorge] Wells, chapter IX, in The First Men in the Moon, London: George Newnes, […], published 1901, →OCLC, page 95:

     I lifted the circular operculum from its place and laid it carefully on the bale.

5. (anatomy) One of several flaps of cerebral cortex covering the insula. (clarification of this definition is needed)

Derived terms

• operculiferous
• operculitis
• preoperculum
• interoperculum
• suboperculum

Related terms

• opercle

Translations

(zoology) covering flap in animals

• Aleut: hmuqatix̂
• Catalan: opercle (ca) m
• Chinese:

  Mandarin: 厴 / 厣 (zh) (yǎn)

• Czech: skřele, žaberní víčko
• Finnish: kiduskansi (fi) (in fish)
• French: opercule (fr) m
• Irish: lannach m, clúidín m
• Italian: opercolo (it) m
• Manx: bleayst f
• Māori: kōrama (in shellfish), kata (of shellfish)
• Persian: درپوش (fa) (darpuš)
• Portuguese: opérculo (pt) m
• Russian: оболо́чка (ru) f (obolóčka), покры́шка (ru) f (pokrýška), жа́берная кры́шка f (žábernaja krýška) (gill cover)
• Spanish: opérculo (es) m
• Tagalog: unya

(botany) lidlike portion on a sporangium or fruit that detaches

• Persian: درپوش (fa) (darpuš)

structure which serves as a cover or lid

Latin

Etymology

Etymology tree

Proto-Indo-European *h₁ep-der.

Proto-Indo-European *h₁épsder.

Proto-Indo-European *h₁épi

Proto-Indo-European *h₂wer-

Proto-Indo-European *-yeti

Latin operiō

Latin -culum

Latin operculum

From operiō (“to close”) + -culum.

Pronunciation

• (Classical Latin) IPA^(key): [ɔˈpɛr.kʊ.ɫũː]
• (modern Italianate Ecclesiastical) IPA^(key): [oˈpɛr.ku.lum]

Noun

operculum n (genitive operculī); second declension

1. cover, covering

Declension

Second-declension noun (neuter).

	singular	plural
nominative	operculum	opercula
genitive	operculī	operculōrum
dative	operculō	operculīs
accusative	operculum	opercula
ablative	operculō	operculīs
vocative	operculum	opercula

Descendants

• → English: opercle, operculum
• → French: opercule
• → Italian: opercolo
• → Portuguese: opérculo
• → Spanish: opérculo

References

• “operculum”, in Charlton T. Lewis and Charles Short (1879), A Latin Dictionary, Oxford: Clarendon Press
• “operculum”, in Charlton T. Lewis (1891), An Elementary Latin Dictionary, New York: Harper & Brothers
• “operculum”, in Gaffiot, Félix (1934), Dictionnaire illustré latin-français, Hachette.
• “operculum”, in Harry Thurston Peck, editor (1898), Harper’s Dictionary of Classical Antiquities, New York: Harper & Brothers