I'm only a first year calculus student so I don't feel too bad asking this probably really dumb question. I noticed in my textbook that the definition of a differential equation was an equation involving the derivatives of a function. Soooo wouldn't that mean that any equation where you can calculate an antiderivative is a differential equation? I don't know if there are any non differentiable equations but if there is not then cant every equation be considered a differential equation? I know differential equations are very important so time is required for me to learn about them and their importance. This is just a curious question I have now. Thanks.