Differential-Difference Equations

equations relating an argument and an unknown function and the latter’s derivatives and increments (differences). For example, y’ = kΔy, where y = y(x) and Δy = y(x + h) - y(x). Substituting the last expression into the initial equation shows that the differential-difference equation is a special case of a differential equation with a diverging argument. Therefore, differential-difference equations are studied within the framework of this wider class of equations.