Illyrian is a group of reputedly Indo-European languages whose relationship to other Indo-European languages as well as to the languages of the Paleo-Balkan group, many of which might be offshoots of Illyrian, is poorly understood due to the paucity of data and is still being examined. The Illyrian languages are often considered to be centum dialects but this is not confirmed as there are hints of satemization. Today, the main source of authoritative information about the Illyrian language consists of a handful of Illyrian words cited in classical sources, and numerous examples of Illyrian anthroponyms, ethnonyms, toponyms and hydronyms. A grouping of Illyrian with Messapian has been proposed for about a century, but remains an unproven hypothesis. The theory is based on classical sources, archaeology, as well as onomastic considerations. Messapian material culture bears a number of similarities to Illyrian material culture. Some Messapian anthroponyms have close Illyrian equivalents. A grouping of Illyrian with Venetic and Liburnian, once spoken in northeastern Italy and Liburnia respectively, is also proposed. The consensus now is that Illyrian was quite distinct from Venetic and Liburnian, but a close linguistic relation has not been ruled out and is still being investigated. Another hypothesis would group Illyrian with Dacian and Thracian into a Thraco-Illyrian branch, and a competing hypothesis would exclude Illyrian from a Daco-Thracian grouping in favor of Mysian. The classification of Thracian itself is a matter of contention and uncertainty. The place of Paeonian remains unclear. Not much has been determined in the study of Paeonian, and some linguists do not recognize a Paeonian area separate from Illyrian or Thracian. The classification of Ancient Macedonian and its relationship to Greek are also under investigation, with sources pointing that Ancient Macedonian is in fact a variation of Doric Greek, but also the possibility of being only related through the localsprachbund. Phrygian, on the other hand, is considered to have been most likely closely related to Greek.
The Albanian language is considered by current linguistic consensus to have developed from one of the non-Greek, ancient Indo-European languages of the region. For more historical and geographical reasons than specifically linguistic ones, the widespread claim is that Albanian is the modern descendant of Illyrian, spoken in much the same region in classical times. Alternative hypotheses hold that Albanian may have descended from Thracian or Daco-Moesian, other ancient languages spoken farther east than Illyrian. Not enough is known of these languages to completely prove or disprove the various hypotheses.
