circle, ring, wheel

ring / (algebra) ring

circum-

a ring or circle shape (such as a ring for a finger, or Saturn's rings) / a hoop (such as for a barrel) / a wheel (as of a vehicle)

an ancient bracelet strung with jewels or bells and worn at the elbow / a longer tube-shaped gauntlet to protect the hand during archery

(obsolete) an ancient jewel or other stone in the shape of a ring

chemistry (branch of natural science)

letter challenging someone to a duel

gender role

(linguistics) "role language": unique language usage serving as a marker of social identity in fictional speech