+A **concave shape** curves inward, like the hollow of a bowl or the interior of a cave. It presents a sunken appearance from an external viewpoint, standing in contrast to a [Convex](/wiki/convex) surface. Such forms are fundamental in fields like [Optics](/wiki/optics) for guiding and focusing light.
+## See also
+- [Curvature](/wiki/curvature)
+- [Geometry](/wiki/geometry)
+- [Surface](/wiki/surface)
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