Concave (adjective)

1. Having a hollow, inward curve, like the interior of a sphere or a bowl.
2. Having a surface that curves inward.

Origin:

Late 16th century: from latin concavus, from con- "together" + cavus "hollow".

Examples:

1. The mirror was concave, distorting the reflection of the objects in front of it.
2. The concave shape of the lens caused light to focus at a single point.
3. The concave surface of the dish was perfect for holding small items.
4. The concave hull of the boat made it unstable in rough waters.
5. The concave design of the seat allowed for a more comfortable and ergonomic experience.