Which term describes a shape that is curved inward?

Which term describes a shape that is curved inward?

• A. Convex
• B. Planar
• C. Spiral
• D. Concave

Answer: (D)

Inward-curving shapes are concave. This describes surfaces or outlines that bend toward their interior, creating an indentation or hollow. A bowl or a cave wall is concave because its surface curves inward. By contrast, a convex shape bulges outward, like the outside of a ball. Planar means flat with no curvature, and spiral describes a winding path around a center, not the direction a surface bends inward. So when the shape curves inward, the correct term is concave.

Inward-curving shapes are concave. This describes surfaces or outlines that bend toward their interior, creating an indentation or hollow. A bowl or a cave wall is concave because its surface curves inward. By contrast, a convex shape bulges outward, like the outside of a ball. Planar means flat with no curvature, and spiral describes a winding path around a center, not the direction a surface bends inward. So when the shape curves inward, the correct term is concave.