annulus

[an-yuh-luh s] /ˈæn yə ləs/
noun, plural annuli
[an-yuh-lahy] /ˈæn yəˌlaɪ/ (Show IPA), annuluses.
1.
a ring; a ringlike part, band, or space.
2.
Geometry. the space between two concentric circles on a plane.
3.
the veil remnant on a mushroom stalk.
4.
a growth ring, as on the cross section of a tree trunk, that can be used to estimate age.
Origin
1555-65; < Latin, variant of ānulus, equivalent to ān(us) ring + -ulus -ule
Examples from the web for annulus
  • The layers of the annulus are woven for maximum absorption.
British Dictionary definitions for annulus

annulus

/ˈænjʊləs/
noun (pl) -li (-ˌlaɪ), -luses
1.
the area between two concentric circles
2.
a ring-shaped part, figure, or space
Word Origin
C16: from Latin, variant of ānulus ring
Contemporary definitions for annulus
noun

See tree ring

Word Origin and History for annulus
n.

1560s, medical, from misspelling of Latin anulus "little ring, finger ring," a diminutive of anus (see anus).

annulus in Medicine

annulus an·nu·lus or an·u·lus (ān'yə-ləs)
n. pl. an·nu·lus·es or an·nu·li (-lī')
A circular or ring-shaped structure.

annulus in Science
annulus
  (ān'yə-ləs)   
Plural annuluses or annuli (ān'yə-lī')

  1. A ringlike figure, part, structure, or marking, such as a growth ring on the scale of a fish.

  2. A ring or group of specialized cells around the sporangia of many ferns. By changing shape in response to variations in humidity, it breaks open the sporangium and then releases the spores with a whipping motion.

  3. The ringlike remains of a membrane (called a veil), found around the stipes of certain basidiomycete mushrooms. The presence or absence of an annulus is often used to identify the species of an individual mushroom.

  4. The figure bounded by and containing the area between two concentric circles.