\begin{definition}[Definition:Differential Equation/Ordinary]
An '''ordinary differential equation''' (abbreviated '''O.D.E.''' or '''ODE''') is a '''differential equation''' which has exactly one independent variable.
All the derivatives occurring in it are therefore ordinary.
The general '''ODE''' of order $n$ is:
:$\map f {x, y, \dfrac {\d x} {\d y}, \dfrac {\d^2 x} {\d y^2}, \ldots, \dfrac {\d^n x} {\d y^n} } = 0$
or, using the prime notation:
:$\map f {x, y, y', y'', \ldots, y^{\paren n} } = 0$
\end{definition}