“Special language domain” (SLD) refers to domains or areas of language use in which linguistic rules may be violated legitimately. The SLD is similar to “free trade zones,” “special administrative regions,” and “special economic zones” in which tariff, executive, and economic regulations may be legitimately violated to an extent. Innovative use in SLD is another major resource for language evolution and language change as well as language contact and language acquisition, since some temporary and innovative forms of usage in SLD may develop beyond the SLD at a later stage to become part of the core system of linguistic rules. Focusing on relevant grammatical phenomena observed in the Chinese language, poetry in various forms, titles and slogans, and Internet language are the three major types of SLD, and their violation of linguistic rules is motivated differently. Furthermore, although core linguistic rules may be violated in SLD, the violations are still subject to certain limits and restrictions. Only some language-particular rules can be violated legitimately in SLD; the principles of Universal Grammar, applicable generally for all human languages, have to be observed even in the SLD. The study of a special language domain provides an ideal and fascinating window for linguists to understand language mechanisms, explain historical change in language, and plausibly predict the future direction of language evolution.