TITLE: Non-ordinary differential equation?
QUESTION [7 upvotes]: Does such a thing exist ?
Can't seem to find anything about it so i was wondering : why bother calling something "Ordinary Differential Equation" if the "Ordinary" part doesn't bring anything to it ?

REPLY [3 votes]: In addition to what others have already said, there are other types of differential equation.
There's the Stochastic Differential Equation, which contain random elements.
There's the Differential-difference equation, which is a blending of differential and difference equations, such as
$$
\frac{d}{dx}f(x)=f(x-1)
$$
So an ordinary differential equation is a differential equation that doesn't have anything "special" about it, it's just a differential equation. It is, quite literally, ordinary.