Thraco-Illyrian is also used as a term merely implying a Thracian-Illyrian interference, mixture or sprachbund, or as a shorthand way of saying that it is not determined whether a subject is to be considered as pertaining to Thracian or Illyrian.
New publications argued that no strong evidence for Thraco-Illyrian exists, and that the two language-areas show more differences than correspondences (Vladimir Georgiev, Ivan Duridanov, Eric Hamp, et al.).
It has also been pointed out that the onomastic studies carried out in the 20th century were conducted through pan-Thracian and pan-Illyrian theoretical approaches, which are considered outdated in current historical linguistics.
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."
[10] 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'.