Do you know when you can't differentiate?

We look at different cases in which it's impossible to differentiate a function at a point.
Do you know when you can't differentiate?
Do you know when you can't differentiate?
Do you know when you can't differentiate?

non-differentiable,non-differentiable function,discontinuous,derivative,lateral limits,cusp,absolute value,vertical tangent,Discover Maths,discovermaths,David Darling,Juan Medina,