difference quotient

Calculus, Mathematical analysis, Mathematics, Sciences The average rate of change of the function f(x) over the interval [a,,a+h]. As h approaches zero, the value of (f(a+h)-f(a))/h approaches the derivative or instantaneous rate of change of f(x) at x=a.

Geometry, Mathematical analysis, Mathematics, Sciences The slope of the secant line passing through the points (a,,f(a)) and (a+h,,f(a+h)). As the horizontal distance h>0 between the points approaches zero, the slope of this secant line approaches the slope of the tangent line to f(x) at x=a, which is equal to the derivative of f(x) at x=a.