Definition of Annulus

1. Noun. A toroidal shape. "A halo of smoke"

Exact synonyms: Anchor Ring, Doughnut, Halo, Ring
Specialized synonyms: Fairy Circle, Fairy Ring
Generic synonyms: Toroid

2. Noun. (Fungi) a remnant of the partial veil that in mature mushrooms surrounds the stem like a collar.
Exact synonyms: Skirt
Category relationships: Fungi, Fungus Kingdom, Kingdom Fungi
Generic synonyms: Plant Part, Plant Structure
Group relationships: Partial Veil

Definition of Annulus

1. n. A ring; a ringlike part or space.

Definition of Annulus

1. Noun. A ring- or donut-shaped area or structure. ¹

2. Noun. (geometry) The region in a plane between two concentric circles of different radius. ¹

3. Noun. (topology) Any topological space homeomorphic to the region in a plane between two concentric circles of different radius. ¹

4. Noun. (astronomy) The ring of the sun not covered by the moon in an annular solar eclipse. ¹

5. Noun. (botany) Structure in a fern that consists of differentially thick-walled cells on a sporangium that bend and distort as a result of drying. ¹

6. Noun. (mycology) The membranous remnants of a partial veil which leaves a ring on the stem of a mushroom. ¹

7. Noun. (context: oil and gas production) The space contained between the centre well bore and any external tubing. Sometimes used for separated gas flow. ¹

¹ Source:

Definition of Annulus

1. a ring or ringlike part [n -LI or -LUSES] : ANNULOSE [adj]

Medical Definition of Annulus

1. A ring-like structure. (18 Nov 2007)

Annulus Pictures

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Lexicographical Neighbors of Annulus

annuloplasty ring
annulospiral ending
annulospiral organ
annulus (current term)
annulus ciliaris
annulus conjunctivae
annulus femoralis
annulus fibrocartilagineus membranae tympani
annulus fibrosus
annulus fibrosus cordis
annulus fibrosus disci intervertebralis
annulus fibrosus of intervertebral disc
annulus haemorrhoidalis
annulus iridis
annulus iridis major

Literary usage of Annulus

Below you will find example usage of this term as found in modern and/or classical literature:

1. The Theory and Practice of Absolute Measurements in Electricity and Magnetism by Andrew Gray (1893)
"For the annulus is made up of elementary annuli, every one of which has the ... The GMD of a finite annulus from a point within its inner bounding circle is ..."

2. The Origin of a Land Flora: A Theory Based Upon the Facts of Alternation by Frederick Orpen Bower (1908)
"One material point is that the formation of the annulus in Ferns at large ... This fact leaves the question of a shifting of the annulus more open than it ..."

3. Proceedings of the Royal Society of London by Royal Society (Great Britain) (1880)
"In seeking an explanation of the appearance of a definite number of lobes in the liquid annulus which is formed at a certain stage of the splash of a drop ..."

4. Organography of Plants, Especially of the Archegoniata and Spermaphyta by Karl Eberhard Goebel (1905)
"The annulus, on the other hand, shows no different orientation. ... The annulus is indicated by a black spot. Il.oneof the dorsiventral ..."

5. Botany by Geological Survey of California, William Henry Brewer, Sereno Watson, Asa Gray (1880)
"... with obliquely beaked operculum, no annulus, and occasionally ... more or less incurved, brownish, not striate when dry ; annulus narrow, persistent. ..."

6. The Study of the Biology of Ferns by the Collodion Method: For Advanced and by George Francis Atkinson (1894)
"A complete annulus in these orders would defeat such an effective dispersion of the spores, since the entire length of the line of cells around the ..."

7. Manual of the Mosses of North America by Leo Lesquereux, Thomas Potts James (1884)
"late, long-lacerate or split to below the middle, erect when dry; annulus very broad, of a triple row of cells. — Scot. Crypt. Fl. t. 123 ; Bryol. Eur. t. ..."

8. Transactions by American Society of Mechanical Engineers (1912)
"Evidently the laws above deduced for the complete annulus apply without modification to the half annulus when its ends are fixed in direction, ..."

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