Definitions for "Annulus"
A ring; a ringlike part or space.
A space contained between the circumferences of two circles, one within the other.
The solid formed by a circle revolving around a line which is the plane of the circle but does not cut it.
The donut-shaped space around the outside of the drill pipe in an open borehole. A cased well has two annular spaces: one between the drill pipe and the casing, the other between the casing and the borehole.
Downhole space between drillstring or casing and borehole wall, or between production tubing and casing, or between surface casing and production tubing and casing.
Free space between the existing pipe and any lining.
In a rolling element bearing, the space between the inner and outer raceways
This is the tough fibrous outer capsule of an intervertebral disc. In the healthy state it encloses and retains the nucleus.
a two-dimensional shape which can be thought of as a disc with a smaller disc removed from its center
Keywords:  botany
A distal segment of the either the antenna or antennula, generally tubular in form.
Keywords:  washer, disk, center, cut
a disk with the center cut out (like a washer
Keywords:  winter, zone, once, marks, growth
Any zone which forms once each year, usually the "winter" growth zone which marks the end of a year of growth.