What is a non-linear...

[robousy]

What makes a PDE non-linear please?

Thanks!!

[arildno]

Do you know what makes an ordinary diff. eq. non-linear?

[Tide]

Do you know what nonlinear means? :)

[HallsofIvy]

Having a non-linear function of the dependent function anywhere in the equation. I suspect arildno and Tide were wondering how you could be studying partial differential equations if you don't know what "non-linear" means!