Concave and convex are often confusing because they look similar and are used to describe shapes. The difference becomes clear once you focus on direction: one curves inward, the other curves outward. Visual thinking—and a simple memory trick—makes these two words easy to tell apart.
Concave vs. Convex
Concave and convex are most commonly used as adjectives to describe the surface or outline of an object.
Concave: Definition and Examples
Concave describes a shape that curves inward, as if the surface is hollowed out.
The word concave contains CAVE. A cave goes inward.
Everyday objects with a concave shape:
- The inside of a spoon
- A bowl
- A cave or tunnel
Concave Examples:
- The inside of the spoon has a concave shape.
- The mirror is concave, so it pulls images inward.
- The garden sat in a concave space between the buildings.
Convex: Definition and Examples
Convex describes a shape that curves outward, bulging away from the center.
If it is not like a cave, it is probably convex.
Everyday objects with a convex shape:
- The back of a spoon
- A balloon
- A road safety mirror
Convex Examples:
- The outside of the spoon is slightly convex.
- The mirror on the street corner is convex to show a wider view.
- The dome has a smooth, convex surface.
Concave vs. Convex Side by Side
- The bowl’s interior is concave, holding the soup inside.
- The bowl’s exterior is convex, curving outward.
- A concave mirror pulls light inward.
- A convex mirror pushes the image outward.
The core difference to remember:
- Concave → curves inward (think CAVE).
- Convex → curves outward.
Final tip:
Imagine standing at the center of the object. If the surface curves toward you, it’s concave. If it curves away from you, it’s convex.
Last Updated on March 2, 2026
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