Introduction: In the context of measuring changes, the notion of partial marginality is used in economics to indicate the partial derivative.
Definition: In economics the partial derivative $z'_x(x,y)$ is called the partial marginal change of $z(x,y)$ with respect to $x$. Similarly, the partial derivative $z'_y(x,y)$ is called the partial marginal change of $z(x,y)$ with respect to $y$.
Definition: In economics the partial derivative $z'_x(x,y)$ is called the partial marginal change of $z(x,y)$ with respect to $x$. Similarly, the partial derivative $z'_y(x,y)$ is called the partial marginal change of $z(x,y)$ with respect to $y$.