concavity

con·cav·i·ty  (kn-kv-t)

n. pl. con·cav·i·ties

1. The state of being curved like the inner surface of a sphere.

2. A surface or structure configured in such a curve: "a perfect concavity of white sand lined with palm . . . trees" Islands.

Thesaurus

Noun	1.	concavity - a shape that curves or bends inward concave shape, incurvation, incurvature solid - a three-dimensional shape dome - a concave shape whose distinguishing characteristic is that the concavity faces downward fossa, pit - a concavity in a surface (especially an anatomical depression) niche, recess, recession, corner - a small concavity bowl, trough - a concave shape with an open top scoop, pocket - a hollow concave shape made by removing something imprint, impression, depression - a concavity in a surface produced by pressing; "he left the impression of his fingers in the soft mud" cup - any cup-shaped concavity; "bees filled the waxen cups with honey"; "he wore a jock strap with a metal cup"; "the cup of her bra" indentation, indenture - a concave cut into a surface or edge (as in a coastline)
	2.	concavity - the property possessed by a concave shape concaveness shape, configuration, conformation, contour, form - any spatial attributes (especially as defined by outline); "he could barely make out their shapes" hollowness - the property of having a sunken area