Total derivative (linear map)
Undergraduate
In multivariable calculus, the total derivative of $f : \reals^n \to \reals^m$ at $x$ is the linear map $Df(x)$ that best approximates $f(x + h) - f(x)$ for small $h$.
Notes
The matrix of a total derivative is the Jacobian matrix.
This is the same concept as the differential. See the meanings of “total derivative”.