 UG includes both invariant principles as well as parameters that allow for variation which place limitations on the form and operations of grammar.Subsequently, research within the Generative Second-Language Acquisition (GenSLA) tradition describes and explains SLA by probing the interplay between Universal Grammar, knowledge of one's native language and input from the target language.Research is conducted in syntax, phonology, morphology, phonetics, semantics, and has some relevant applications to pragmatics.