Four-gradient

In differential geometry, the four-gradient (or 4-gradient) ${\displaystyle {\boldsymbol {\partial }}}$ is the four-vector analogue of the gradient ${\displaystyle {\vec {\boldsymbol {\nabla }}}}$ from vector calculus.

In special relativity and in quantum mechanics, the four-gradient is used to define the properties and relations between the various physical four-vectors and tensors.