Annulus

Annulus (or anulus) or annular indicates a ring- or donut-shaped area or structure. It may refer to:

Human anatomy

 * Anulus fibrosus disci intervertebralis, spinal structure
 * Annulus of Zinn, a.k.a. annular tendon or anulus tendineus communis, around the optic nerve
 * Annular ligament (disambiguation)
 * Digitus anularis, a.k.a. ring finger
 * Anulus ciliaris, a.k.a. ciliary body
 * Anulus femoralis, a.k.a. femoral ring
 * Anulus inguinalis superficialis, a.k.a. superficial inguinal ring
 * Anulus inguinalis profundus, a.k.a. deep inguinal ring
 * Anuli fibrosi cordis, a.k.a. fibrous rings of heart
 * Anulus umbilicalis , a.k.a. umbilical ring

Other

 * Annulus (construction), outer gear ring in an epicyclic gearing
 * Annulus (botany), structure on fern and moss sporangia
 * Annular lake, a ring-shaped lake caused by meteor impact
 * Annulus (mathematics), the shape between two concentric circles
 * Annulus (mycology), structure on mushroom
 * Annulus (firestop), site of construction issue
 * Annular piston, a ring-shaped piston
 * Annulus (well), void between concentric cylinders
 * Annular blowout preventer, device for sealing oil and gas wells
 * Annulation, type of ring-producing chemical reaction