Curved like the inner surface of a sphere or bowl.
Hollow; empty.
Satisfying the property that all segments connecting two points on the function's graph lie below the function.
Not convex; having at least one internal angle greater than 180 degrees.
A playing card made concave for use in cheating.
One of the celestial spheres of the Ptolemaic or geocentric model of the world.
An indentation running along the base of a surfboard, intended to increase lift.
An element of a curved grid used to separate desirable material from tailings or chaff in mining and harvesting.
The vault of the sky.
An indented area on the top of a skateboard, providing a position for foot placement and increasing board strength.
A concave surface or curve.
To render concave, or increase the degree of concavity.
Spherical.
Of or relating to the heavenly orbs, or to the sphere or spheres in which, according to ancient astronomy and astrology, they were set.