Meaning of annulus in English:


Pronunciation /ˈanjʊləs/

nounplural noun annuli/ˈanjʊlʌɪ/ /ˈanjʊliː/

  • 1 technical A ring-shaped object, structure, or region.

    ‘Channel incorporation was typically achieved within a few minutes after ‘brushing’ the membrane fraction across the annulus with fresh lipids to form a new bilayer.’
    • ‘The tympanic annulus must be completely visible.’
    • ‘The fibrillar collagens also change across the disc, with the nucleus containing only type II collagen while both types I and type II are found in the annulus.’
    • ‘The position of the annulus is a key character used to differentiate lineages within the clade.’
    • ‘The calcification extended into the mitral annulus.’
    • ‘It is possible that the ligamenta flava provide some resistance to flexion and so, like the posterior longitudinal ligament, protect the posterior annulus.’
    • ‘Many derived mosses have yet another control on spore dispersal: a peristome with peristome teeth arranged around an annulus.’
    • ‘Within this recess we would find the curved remnants of the angular (the tympanic) which actually form the tympanic annulus.’
    • ‘The structure of the annulus provides stability, and the elastic nature of the nucleus allows it to change shape to distribute forces equally along the cervical spine.’
    • ‘A beamsplitter mixes the returning measurement beam with the collimated local beam; the inner core component is directed to the target detector and the outer annulus goes to the reference detector.’
    • ‘Mitral valve prolapse occurs when varying portions of one or both leaflets of the mitral valve extend or protrude abnormally above the mitral annulus into the left atrium.’
    • ‘No defect was detected in the relocation of the paired centrioles to abut the nuclear membrane or in the initial formation of the annulus.’
    • ‘Exploration of the right ear suggested a fistula in the anterior annulus of the oval window, with perilymphatic fluid leak visible on Valsalva at middle ear exploration.’
    • ‘The cells of the outer annulus are thin and extended along the collagen fibrils, rather like tendon cells.’
    • ‘The pipette microchamber introduces a mechanical constraint around the annulus where the pipette tip contacts the plasma membrane.’
    • ‘At the other end, headgroups of phospholipids should form an annulus through which permeating ions must pass to cross the membrane.’
    • ‘The inner and outer margins of the annulus were observed to bulge outwards but when the nucleus was removed the inner margins bulged inwards.’
    • ‘The nucleus eventually no longer acts hydrostatically, thus the annulus and endplate are exposed to high point stresses which might lead to the cracks and fissures seen in degenerate discs.’
    • ‘Under these circumstances neither the annulus nor the lipid membrane will be situated symmetrically around the edges of the orifice.’
    • ‘At a lateral optical resolution of 0.4 m FWHM the bright fluorescence of the lipid annuli outshone the very weak fluorescence of the bilayer membranes.’
    1. 1.1Mathematics A plane figure consisting of the area between a pair of concentric circles.
      ‘A theorem is proved that delineates criteria for the radii of the annulus of the zeros in the complex plane of the generating function for factorial moments as it applies to high-energy charged-hadron multiproduction.’
      • ‘In this case, weighting was used to adjust for the fact that at increasing distances from a seed there will be an increasing number of possible maternal trees simply due to the greater two-dimensional area of an annulus of a fixed width.’
      • ‘In this paper, we find necessary and sufficient conditions for the stability of a family of annular, complex polynomials with the possibility of including a center polynomial. The proposed results can be modified to solve the disk problem by simply equating the inner radius of the annuli to zero.’
      • ‘An annulus is the shape made by the space between two concentric circles. Much geometrical pattern-work uses the annulus. It is sometimes called a ring.’
      • ‘The width of an annulus is the difference between the radii of its two defining circles.’
      circle, disc, circlet


Mid 16th century from Latin anulus, annulus.