crescent
crescent moon
fifty percent
fifty-fifty
half
half circle
half-and-half
half-moon
hemicycle
hemisphere
horseshoe
lunula
lunule
mediety
meniscus
moiety
quadrant
scythe
sector
semicircumference
semisphere
sextant
sickle
plane figure
two-dimensional figure
amphitheatre
arc
circle
circumference
concourse
declivity
ellipse
expanse
half-circle
huddle
pyramid
rectangle
stockade
triangle
wedge