annulus
Doughnut-shaped region mathematically
An annulus is a ring-shaped structure—the region between two concentric circles.
The term appears in mathematics, anatomy, and biology: Calculate the area of the annulus, the annulus of a mushroom.
In anatomy, it often refers to ring-shaped tissues or openings, as in the heart's valve annuli.
Closed curve shape
- circleCurved closed shape
- torusDoughnut-shaped solid
- diskFlat circular object
- circumferenceCircle's outer measurement
diameter · radius · arc · sector · chord · concentric · ellipse · oval
Closed curve shape
- bandGroup playing music together
- washerSpacer ring for fasteners
- gasketMechanical leak preventer
- sealAuthentication stamp or mark
flange · collar · sleeve · spacer · grommet · bushing · bearing · o-ring
Circular outer boundary
- edgeBoundary or sharpness
- borderOuter edge or limit
- marginEdge of a page
- perimeterShape's outer edge length
circumference · outer · inner · fringe · limit · enclosure · periphery · surround
Curved celestial path
corona · penumbra · umbra · transit · occultation · photosphere · chromosphere · sun
ring
Closed curve shape
circumference · diameter · radius · arc · sector · chord · concentric · ellipse · oval · curvature
ring
Closed curve shape
seal · flange · collar · sleeve · spacer · grommet · bushing · bearing · o-ring · fitting
rim
Circular outer boundary
perimeter · circumference · outer · inner · fringe · limit · enclosure · periphery · surround · encircle
orbit
Curved celestial path
celestial · corona · penumbra · umbra · transit · occultation · photosphere · chromosphere · sun · moon
disc
Flat circular object
- intervertebralBetween adjacent spine segments
- spinalOf the backbone
- cartilageFlexible connective body tissue
membrane · valve · cardiac · mitral · tricuspid · aortic · tissue · ligament · collagen · herniation
dendrochronology
Dating via growth rings
bark · trunk · cross-section · annual · seasonal · age · wood · increment
- circlesfull circle, circle, radius, circumference, pie chart
- circular thingscircle, ring, loop, hula hoop, basketball hoop
- geometric shapessphere, triangle, square, cone, rectangle
- shapescircle, square, triangle, rectangle, oval
- surfacessurface, sphere, cone, torus, plane
- mycologymycology, mushroom, toadstool, mycelium, mycorrhizae