environment; circumstance
annulation; ring shape; loop shape
links; chain; shackle; linking
atoll; circular coral reef
looking around; looking about
circumzenithal arc; cicumzenith arc
umwelt; self-centered world
cyclic compound; ring compound
ball-and-ring method; ring-and-ball test
polycyclic aromatic hydrocarbon; PAH
ring inversion; ring flip
signet ring (in medical contexts, e.g. signet ring cell)
clasp or ring for attaching a pendant to a chain
Newton's rings (interference pattern seen when a convex lens is placed on another surface)
Artinian ring; Artin ring
Artinian ring; Artin ring
fairy ring; mushroom ring