> “Smooth” is a term of art in math that means continuously differentiable infinitely many times. These functions include, as a subset, functions which are diff

> “Smooth” is a term of art in math that means continuously differentiable infinitely many times. These functions include, as a subset, functions which are differentiable once. Of course you knew what you meant, but, for anyone who's confused, the containment goes the other way.