Calculus of moving surfaces
The calculus of moving surfaces (CMS) is an extension of the classical tensor calculus to deforming manifolds. Central to the CMS is the tensorial time derivative ∇ ˙ {\displaystyle {\dot {\nabla }}} whose original definition was put forth by Jacques Hadamard.
Source: Wikipedia — Calculus of moving surfaces (CC BY-SA 4.0)