# How does Leibniz notation work?

$\frac{d}{\mathrm{dx}}$ represents the derivative with respect to $x$.
$y ' = \frac{\mathrm{dy}}{\mathrm{dx}}$
$y ' ' = \frac{d}{\mathrm{dx}} \left(\frac{\mathrm{dy}}{\mathrm{dx}}\right) = \frac{{d}^{2} y}{\mathrm{dx}} ^ 2$,