The SHOWNL command will cause LINGO to 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 SHOWNL command is helpful in tracking down a model's nonlinearities.