[tylerhou]

There is nothing wrong with using a non-linear model, though; x^2 or x^3 regressions make sense on many datasets.

Non-continuous is also not the perfect terminology, but I argue that it is more precise than non-linear: the chief idea being that the model "changes unpredictably."

[kccqzy]

Sure you can argue things however you want, if you also decide to ignore hundreds of years of mathematical terminology.