Concave vs Convex

CONCAVE vs CONVEX: Interesting Differences between Convex vs Concave

Concave vs Convex! These two words can easily be mixed up because of their similarity: both their form and meaning are similar. They can be seen in your daily life, but they are most often found in physics or math classes.


As I said before, these words have a similar meaning: they talk about the type of curvature an object has. Therefore, convex means “having an outline or surface that curves outwards”, while concave means “having an outline or surface that curves inwards”. With this in mind, the difference is clear, in and out, but how do concave objects actually look like?

When to Use Concave

If you drop a plate but it doesn’t break fully, it’s just missing a piece, then the shape of the plate would be a concave shape. If you have a ping pong ball and you step on it, denting it in the process, then the shape of the ball would also be concave. So concave is always used for curves that go inwards. In math, a function is concave if no line segment joining two points on the graph lies above the graph at any point (there are formulas for this, I just gave you the definition).


  • Did you know that your bathtub is actually CONCAVE?
  • If the second derivative of the function is negative, then the function is CONCAVE.

When to Use Convex

If your soccer ball or tire has a bulge, then you can call them convex. If you ever see a square you can call it convex too. So convex means that there exists a curve that goes outwards. A convex function is similar to a concave function, but this time there should be no segment joining two points on the graph that lies below the graph.


  • The doctor told me to use CONVEX lenses to improve my sight.
  • CONVEX functions are cool, they look like a bucket.

Tips for the Differences between Concave vs Convex

There is no obvious reason for why concave is concave and convex is convex, so you can get them mixed up really easily. I did that in math class all the time. I figured out a trick that saved my life (and grades). Imagine a mountain with a cave at the bottom, just like in cartoons. Now, only draw the outlines. What you get is a concave shape. Simple, right?

Concave vs Convex Examples:

  • The null test method for concave conic surface is discussed.
  • The palm of one’s hand is slightly concave.
  • The graph of a concave function is always below its tangent.
  • He extended his method to test the figure of concave mirrors.
  • The telescope contains a large convex mirror to collect the light.
  • Convex function is an significant type of function.
  • convex lens is used to concentrate rays of light.
  • The surface of the space key can be flat or convex.

Difference between Convex vs Concave | Image

Concave vs Convex

Convex vs Concave: How to Use Concave vs Convex Correctly?

Notify of
Inline Feedbacks
View all comments
Would love your thoughts, please comment.x