"With respect to x" indicates that we are finding the derivative of a function with respect to x, focusing on how it changes as x varies while treating other variables as constants.
Related terms
Partial Derivative: A partial derivative measures how a function changes with respect to one variable while keeping all others constant.
Total Derivative: The total derivative of a multivariable function measures its overall rate of change with respect to all variables.
The variable in a function that can be freely chosen or varied without being dependent on any other variable. In this case, x is the independent variable.