There are at least two meanings of the term "total derivative" in mathematics.
The first is as an alternate term for the convective derivative.
The second meaning of total derivative is the derivative with respect to of the function that depends on the variable not only directly but also via the intermediate variables . It can be calculated using the formula
The total derivative of a function with respect to is implemented in the Wolfram Language as Dt[f[t, x, y, ...], t].