Thuringian is an East Central German dialect group spoken in much of the modern German Free State of Thuringia north of the Rennsteig ridge, southwestern Saxony-Anhalt and adjacent territories of Hesse and Bavaria. It is close to Upper Saxon spoken mainly in the state of Saxony, therefore both are also regarded as one Thuringian-Upper Saxon dialect group. Thuringian dialects are among the Central German dialects with the highest number of speakers.
the weakening of consonants of Standard German (the lenition of the consonants "p," "t," and "k"),
a marked difference in the pronunciation of the "g" sound (which is most common in the areas of North Thuringia and Saxony-Anhalt areas),
and a highly-idiosyncratic, melodic intonation of sentences.
The second German consonant shift manifested itself in a manner different from that elsewhere in the areas that spoke High German. In many words, "b" is pronounced as "w" or "f" would be in Standard German. For example, the word aber (but) is pronounced as "aḅer". The Thuringian dialect has advanced beyond the stage of basilect.
Furthermore, its linguistic border to the north coincides with the Uerdingen line, to the west it coincides with the Germerscheim line. Its southern border to East Franconian is demarcated by a number of morphological criteria:
the shape of the diminutive suffix (-chen vs. -lein)
the shape of the infinitival suffix (-en vs. -e),
and the retention of stem forming /n/ (Mann vs. Mo ‘man’).
Its eastern border to Upper Saxon is demarcated by the shape of infinitival suffix (-en vs. -e). Furthermore, Thuringian also requires a specific element to appear, namely enn, comparable to the South Hessian and Bavarian question particle ‘n, but in contrast to these dialects, enn in Thuringian is not restricted to wh-questions. enn necessarily appears in all questions.
↑ROSENKRANZ, HEINZ (1964): Der Thüringische Sprachraum. Haale (Saale): VEB Niemeyer
↑Pankau, Andreas. "The question particle enn in Thuringian and its implications for the analysis of wh. drop." Speyer, Augustin/Julia Hertel (Hg.): Syntax aus Saarbrückener Sicht 3 (2020): 255-280.
Ostmitteldeutsch. In: Lexikon der Germanistischen Linguistik. Herausgegeben von Hans Peter Althaus, Helmut Henne, Herbert Ernst Wiegand. 2nd ed., Max Niemeyer Verlag Tübingen, 1980 (1st ed. 1973), p. 474ff., here p. 474–477
Ostmitteldeutsche Dialektologie. In: Ludwig Erich Schmitt (ed.): Germanische Dialektologie. Festschrift für Walther Mitzka zum 80. Geburtstag. I. (Zeitschrift für Mundartforschung. Beihefte, Neue Folge 5.) Franz Steiner Verlag GmbH, Wiesbaden 1968, p. 105–154, here p. 132 and 143 [uses the terms ostmitteldeutscher Dialektraum on the 1st level, then on the 2nd level (adjective ending in -er) Dialektverband and on the 3rd (adjective ending in -e) Dialektgruppe]
↑C. A. M. Noble: Modern German Dialects. Peter Lang, New York / Berne / Frankfort on the Main, p. 131
↑Karl Spangenberg: Thuringian. In: Charles V. J. Russ (ed.): The Dialects of Modern German: A Linguistic Survey. Routledge, first published 1990, reprinted 2000, transferred to Digital Printing 2006, [ISBN 0-415-00308-3], p. 265–289, here 267–278 (in the chapter Dialect Structure and Dialect Features) [it also mentions some East Franconian]