a variety of bilingualism resulting from the prolonged existence of two languages in the same territory. An adstratum arises from the effect which the language of the newcomers has on that of the native population; the former is at first preserved in the capacity of a neighbor language. Linguistic changes associated with adstratum transcend the mere borrowing of individual words and concern the very structure of the language (phonetic, grammatical, lexical). As a result of adstratum, linguistic signs common to genetically unrelated languages may appear.