Concave or Convex?? The easiest way to see this is that concave shapes look like they “cave” in. However, in math we want to have a precise definition of our terms. Saying “Look at it! It caves in!” usually isn’t going to cut it. There are a few different ways to define convex and concave, but I think this is the one that is most appropriate for third grade: In a convex shape, all diagonals lie within the shape. In a concave shape, at least one diagonal is outside of the shape. Another definitio

Kaltenborn Concave-Convex Rule