Linked from

The 8 pages that link to Weak derivative, each with the reason it gives.

• GradientRelated: Weak gradients let nonsmooth functions enter many differential equations.

• Sobolev inequalityRelated: Sobolev inequalities apply even when classical derivatives do not exist.

• Agmon's inequalityRelated: Sobolev norms measure weak derivatives, including for nonsmooth functions.