Extraneus, a term used in the law of succession during the first half of the XIVth century. The development of the Roman Law in the twelfth and thirteenth century's in the Law universities from the western european space, generated the assimilation of some Roman Law terminology, having in some cases the same connotation or a changed one, and the introduction of those words in the medieval documents. The term extraneus had been used in the Roman Law from the VIth century for defining the heir which was outside the authority of the parents. The term was used for the first time in medieval Hungary in the laws of king Andrew III, and the definition is exactly like that from the sixth century for the heirs which had the extraneus status. The laws of succession from the early Hungarian kings in the eleventh and thirteenth century's was still used, but with the introduction of the new term, extraneus. The use of this new term, extraneus, in the documents which emanated from the juridic authority's of Transylvania, for the juridic disputes in this administrative space, demonstrate an connection of Transylvania with the latest educational developments in the juridic domain from the European universities, and the introduction of these developments in real juridic cases from the first half of the fourteenth century.