Annulus

Annulus (Latin annulus " the Ring", plural annuli ) referred to:

Annulus ( microscopy), an octagonal electron-dense region of the nuclear envelope of a cell in the electron
Annulus (muscle ), a ring-shaped muscle field about the Nautilus or the beard worms
Annulus (skin), ring-shaped skin fold; several annuli yield a girdling of the body
Annulus ( mycology ), the ring on the stem of many Basidiomycetes
Annulus occipital, a neck ring on the back of the head with trilobites
Annulus ( Ichthyology ), on the scales of many Teleostomen: the annual ring
Annulus pontificalis, a bishop's ring
Annulus ( deep drilling ), the space between the casing and the surrounding formation, respectively, a further casing
A ring gear
An annulus