The
Vardar,
South Morava and
Great Morava rivers are generally considered to approximate the border between the Illyrian and Thracian spheres, in the west and east respectively. However, Thracian and Illyrian did not have a clear-cut frontier. There was also, clearly, significant interaction between the Illyrian and Thracian spheres, with some Thracian groups occupying the Illyrian sphere and vice versa; the identity of some groups as Illyrian or Thracian has also remained unclear, or, in some instances, a Thraco-Illyrian mix has been proposed. Such factors reinforce the impression that many similarities between the Illyrian and Thracian lexes resulted from
language contact. Other scholars, such as Romanian linguist and historian , argue that there were major similarities between Illyrian and Thracian and so a shared, ancestral linguistic branch is probable, rather than them forming a
sprachbund. Among the Thraco-Illyrian correspondences noted by I. I. Russu are the following: Not many Thraco-Illyrian correspondences are definite, and a number may be incorrect, even from the list above.
Sorin Paliga (2002) however states: "According to the available data, we may surmise that Thracian and Illyrian were mutually understandable, e.g. like
Czech and
Slovak, in one extreme, or like
Spanish and
Portuguese, at the other." Other linguists however argue that Illyrian and Thracian were different Indo-European branches which later converged through contact. It is also of significance that
Illyrian languages still have not been classified whether they were
centum or
satem language, while it is undisputed that Thracian was a
satem language by the Classical Period (the satem nature of proto-Thracian is disputed, Olteanu 2002). Due to the fragmentary attestation of both Illyrian and
Thraco-Dacian, the existence of a Thraco-Illyrian branch remains controversial. Evidence of a Thraco-Illyrian branch has also been sought in the
Albanian language, which has been claimed to have developed from either an Illyrian language with Thraco-Dacian influences or a Thraco-Dacian language with Illyrian influences. However, the arguments for such claims tend to be circular: for example, the kinship of the Albanian with the Thracian is affirmed by attributing Albanian traits to the Thracian. Due to the paucity of written evidence, what can be said with certainty in current research is that on the one hand a significant group of
shared Indo-European non-Romance cognates between Albanian and Romanian indicates at least contact with the 'Daco-Thraco-Moesian complex', and that on the other hand there is some evidence to argue that Albanian is descended from the 'Illyrian complex'. On the basis of shared features and innovations, Albanian is grouped together with
Messapic in the same branch in the current phylogenetic classification of the
Indo-European language family, called '
Albanoid' or 'Illyric'. ==See also==