universal grammar

n. The term universal grammar (UG) describes the set of universal principles that license the grammars of all languages. Knowledge of these principles is argued to be innate, part of the human genetic endowment. Acquisition of a language-specific grammar therefore involves using input to determine the language-specific settings of the universal principles dictated by UG for the particular language being learned. For example, UG licenses languages that form questions by movement of the question (or wh-) element to the beginning of the sentence (such as English), as well as languages where the whelement remains in situ (such as Chinese). However, forming questions, say, by flipping the linear order of words in a sentence falls beyond the range of languages licensed by UG. Arguments for the existence of UG rely on evidence from language acquisition: children acquire a highly complex linguistic system in a relatively brief amount of time, without explicit instruction and from impoverished input that vastly underrepresents what they eventually know about their language. Proponents of UG have proposed that children are able to learn such a complex system because most of it is available to them a 
priori, from birth. – EMF