# Order of Differential Equation/Examples/Second Order

The following ordinary differential equations are of the $2$nd order:
$\dfrac {\d^2 y} {\d x^2} = \dfrac 1 {1 - x^2}$
$\map {f'} x = \map {f''} x$
$y'' + \paren {3 y'}^3 + 2 x = 7$