The upside-down capital delta symbol , also called "nabla" used to denote the gradient and other vector derivatives.

The following table summarizes the names and notations for various vector derivatives.

The upside-down capital delta symbol , also called "nabla" used to denote the gradient and other vector derivatives.

The following table summarizes the names and notations for various vector derivatives.

Weisstein, Eric W. "Del." From *MathWorld*--A
Wolfram Web Resource. https://mathworld.wolfram.com/Del.html