Which term describes a surface that is depressed or hollow?

• A. Convex
• B. Concave
• C. Flat
• D. Curved

Answer: (B)

When describing a surface shape, concave means it curves inward, creating a hollow or depressed area like the inside of a bowl. This inward curvature is what the term conveys, so a surface that appears sunken or hollow fits concave best. In contrast, convex describes outward bulging, flat means no curvature at all, and curved is too general because it doesn’t specify whether the curve goes inward or outward. So the term that precisely matches a depressed or hollow surface is concave.