concave

Concave describes an inward curve; its opposite, convex, describes a curve that bulges outward. They are used to describe gentle, subtle curves, like the kinds found in mirrors or lenses.

A valley is a concave curve, a mountain is a convex curve—you can remember this by thinking that things that vex you tend to stick out, and that caves tend to be holes that go in, like valleys or innie belly buttons. If you want to describe a bowl, you might say there is a large blue spot on the center of the concave side.

Definitions of concave
1

adj curving inward

Synonyms:
acetabular, cotyloid, cotyloidal
of the cup-shaped socket that receives the head of the thigh bone
biconcave, concavo-concave
concave on both sides
boat-shaped
having a concave shape like a boat
bowl-shaped
having a concave shape with an open top like a bowl
bursiform, pouch-shaped, pouchlike, saclike
shaped like a pouch
concavo-convex
concave on one side and convex on the other with the concavity being greater than the convexity
cuplike
resembling the shape of a cup
cupular, cupulate
shaped like (or supporting) a cupule
dish-shaped, dished, patelliform
shaped like a dish or pan
planoconcave
flat on one side and concave on the other
recessed
resembling an alcove
saucer-shaped
having a concave shape like a saucer
umbilicate
depressed like a navel
urn-shaped
having a concave shape like an urn
intrusive
thrusting inward
Antonyms:
bulging, convex
curving or bulging outward
bell-shaped
having a convex shape that resembles a bell
biconvex, convexo-convex, lenticular, lentiform
convex on both sides; shaped like a lentil
broken-backed, hogged
(of a ship) so weakened as to sag at each end
convexo-concave
convex on one side and concave on the other with the convexity being greater than the concavity
gibbose, gibbous
(used of the moon) more than half full
helmet-shaped
having the convex shape of a helmet
planoconvex
flat on one side and convex on the other
umbel-like, umbellate
resembling an umbel in form
protrusive
thrusting outward
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