concavity
The convexity of his glasses was so slight that you could barely notice it.
The stomach is shaped like a banana with the convexity facing downwards.
She removed a little material around the edge to give it some convexity.

SMART Vocabulary: related words and phrases

Geometry: properties of circles & curves
amplitude
arched
bore
circularity
circumferential
concave
concavity
concentric
concentrically
conic
curvy
domed
eccentric
girth
lenticular
lentiform
osculate
parabolic
rectifiable
spiral