A differential equation is an equation that contains at least one derivative.
A differential equation is an equation that contains at least one derivative. A derivative is the rate of change in a function with respect to changes in a variable. For example, Newton's second law states that force equals mass times acceleration ($F = ma$), but acceleration is the rate of change in velocity over time ($a = dv/dt$), thus:
$$
F = m\frac{dv}{dt}
$$
