E-language has been used to describe the application of artificial systems, such as in calculus, set theory and with natural language viewed as sets, while performance has been used purely to describe applications of natural language. Between I-Language and competence, I-Language refers to our intrinsic faculty for language, competence is used by Chomsky as an informal, general term, or as term with reference to a specific competency such as "grammatical competence" or "pragmatic competence".
