annulus

English

Noun

annulus (plural annuluses or annuli)

1. A ring- or donut-shaped area or structure.
2. (geometry) The region in a plane between two concentric circles of different radius.
3. (topology) Any topological space homeomorphic to the region in a plane between two concentric circles of different radius.
4. (astronomy) The ring of the sun not covered by the moon in an annular solar eclipse.
5. (botany) Structure in a fern that consists of differentially thick-walled cells on a sporangium that bend and distort as a result of drying.
6. (mycology) The membranous remnants of a partial veil which leaves a ring on the stem of a mushroom.
7. (oil and gas production) The space contained between the centre well bore and any external tubing. Sometimes used for separated gas flow.

Synonyms

• (topological space): cylinder

Hyponyms

• (ring-shaped structure): torus

Derived terms

• annulate
• annulation

Translations

ring-shaped structure

• Aragonese: aniello (an) m
• Asturian: aniellu (ast) m
• Catalan: anell (ca) m
• Corsican: anellu (co) m
• French: anneau (fr) m
• Galician: anel (gl) m

• Italian: anello (it) m
• Latin: anulus (la) m
• Portuguese: anel (pt) m
• Romanian: inel (ro) n
• Spanish: anillo (es) m

the region in a plane between two concentric circles of different radius

• Spanish: corona circular (es) f

astronomy: the ring of the sun not covered by the moon

• Navajo: ahééjiichįįʼ

• Spanish: corona solar (es) f

botany: structure in a fern

• Hungarian: annulusz (hu)

mycology: membranous remnants

• Spanish: anillo (es) m

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Latin

Noun

ānnulus (genitive ānnulī); m, second declension

1. Alternative form of ānulus.

Inflection

Number	Singular	Plural
nominative	ānnulus	ānnulī
genitive	ānnulī	ānnulōrum
dative	ānnulō	ānnulīs
accusative	ānnulum	ānnulōs
ablative	ānnulō	ānnulīs
vocative	ānnule	ānnulī