annulus

an·nu·lus

noun \ˈan-yə-ləs\

plural an·nu·li\-ˌlī, -(ˌ)lē\ also an·nu·lus·es

Definition of ANNULUS

1

: ring

2

: a part, structure, or marking resembling a ring: as a : a line of cells around a fern sporangium that ruptures the sporangium by contracting b : a growth ring (as on the scale of a fish) that is used in estimating age

Origin of ANNULUS

Medieval Latin, from Latin anulus finger ring, from anus ring — more at anus

First Known Use: 1563