Universal grammar (UG) is a linguistic theory that states the ability to acquire language is genetically specified for human beings. That is, according to the UG theory, acquiring language is based on a set of principles that apply to all natural languages and to parameters that vary from one language to another. These principles and parameters are innately available to humankind. The theory dates back to the 1950s when it was proposed by linguist Noam Chomsky. According to Chomsky, all languages share common principles—also known as “linguistic universals”—and language variation is understood as a variation in setting certain language parameters.

In this view, all languages share common universals (i.e., principles and parameters), although not all languages have to employ all the common universals. These universals are ...