Linear and nonlinear solve for steady state tutorials

[bclyons12]

In the tutorials, the Steady State Heat Equation is described as a nonlinear problem, but it's fully linear. Why is this solved using NonlinearSolve.solve?

Conversely, the Steady state of SIS problem is nonlinear, with factors like S(t, x) * I(t, x) / (S(t, x) + I(t, x)). Why does this one not use NonlinearSolve?

[xtalax]

Nonlinear refers to the type of systems of equations that are used to solve in each case. Steady state problems are nonlinear root finding problems, not ODEs hence they are solved with NonlinearSolve. Problems with time are typically lowered to ODEs, hence they use OrdinaryDiffEq