If you choose the Display Nonlinear Rows option of the Generate command, then LINGO will generate the model and then display only those rows that contain nonlinearities.  Please refer to the Types of Constraints section for a discussion of linear vs. nonlinear expressions.

In general, one would prefer to always have purely linear models.  Linear models solve faster and will always converge to a global solution.  Therefore, when developing a model, you will be interested in carefully evaluating nonlinearities to see if they can either be eliminated or rewritten in a linear fashion.  The Display Nonlinear Rows is helpful in tracking down a model's nonlinearities.