O
annular muscle
annulus
areola
aureole
chaplet
circle
circuit
circumference
circus
closed circle
corona
coronet
crown
cycle
diadem
discus
disk
eternal return
fairy ring
garland
glory
halo
lasso
logical circle
loop
looplet
magic circle
noose
orbit
radius
ring
round
roundel
saucer
sphincter
vicious circle
wheel
wreath