Differential refers to small changes in variables. It doesn't mean anything in itself. In economics, calculus usually refers to the derivative and integral of a function. Derivative is a very meaningful quantity. It is the influence of the change of one quantity on the change of another quantity. For example, if the derivative of cost function to output represents marginal cost, then it is the impact of unit output change on cost. The meaning of integral is much more complicated. Different places have different meanings and cannot be generalized. For example, in a perfectly competitive market, the definite integral of (demand function-price) is consumer surplus; And the definite integral of (supply function-price) is producer surplus. ...