The Thracian language or languages were spoken in what is now Bulgaria,^[9][10] Romania, North Macedonia, Northern Greece, European Turkey and in parts of Bithynia (North-Western Asiatic Turkey).

Little is known for certain about the Thracian language, since no text has been satisfactorily deciphered. Some of the longer inscriptions may be Thracian in origin but they may simply reflect jumbles of names or magical formulas.^[11]

Enough Thracian lexical items have survived to show that Thracian was a member of the Indo-European language family.

Besides the aforementioned inscriptions, Thracian may be attested through personal names, toponyms, hydronyms, phytonyms, divine names, etc. and by a small number of words cited in Ancient Greek texts as being specifically Thracian.^{[12][unreliable source?]}

There are 23 words mentioned by ancient sources considered explicitly of Thracian origin and known meaning.^[13][14] Of the words that are preserved in ancient glossaries, in particular by Hesychius, only three dozen can be considered "Thracian". However, Indo-European scholars have pointed out that "even the notion that what the ancients called "Thracian" was a single entity is unproven."^[15] The table below lists potential cognates from Indo-European languages, but most of them have not found general acceptance within Indo-European scholarship. Not all lexical items in Thracian are assumed to be from the Proto-Indo-European language, some non-IE lexical items in Thracian are to be expected.

The following are the longest inscriptions preserved. The remaining ones are mostly single words or names on vessels and other artifacts. No translation has been accepted by the larger Indo-European community of scholars.^[29]

Only four Thracian inscriptions of any length have been found. The first is a gold ring found in 1912 in the village of Ezerovo (Plovdiv Province of Bulgaria); the ring was dated to the 5th century BC.^[30] The ring features an inscription in a Greek script consisting of 8 lines, the eighth of which is located on the rim of the rotating disk; it reads without any spaces between: ΡΟΛΙΣΤΕΝΕΑΣΝ / ΕΡΕΝΕΑΤΙΛ / ΤΕΑΝΗΣΚΟΑ / ΡΑΖΕΑΔΟΜ / ΕΑΝΤΙΛΕΖΥ / ΠΤΑΜΙΗΕ / ΡΑΖ // ΗΛΤΑ

Dimitar Dechev (Germanised as D. Detschew) separates the words as follows:^[31][32]

A second inscription, hitherto undeciphered, was found in 1965 near the village of Kyolmen [bg], Varbitsa Municipality, dating to the sixth century BC. Written in a Greek alphabet variant, it is possibly a tomb stele inscription similar to the Phrygian ones; Peter A. Dimitrov's transcription thereof is:^[33]

ΙΛΑΣΝΛΕΤΕΔΝΛΕΔΝΕΝΙΔΑΚΑΤΡΟΣΟ^[34]

ΕΒΑ·ΡΟΖΕΣΑΣΝΗΝΕΤΕΣΑΙΓΕΚΟΑ^[35]

ΝΒΛΑΒΑΗΓΝ^[34]

i.e.

ilasnletednlednenidakatroso

eba·rozesasnēnetesaigekoa

nblabaēgn

A third inscription is again on a ring, found in Duvanlii [bg], Kaloyanovo Municipality, next to the left hand of a skeleton. It dates to the 5th century BC. The ring has the image of a horseman^[36] with the inscription surrounding the image.^[37] It is only partly legible (16 out of the initial 21):

The word mezenai is interpreted to mean 'Horseman', and a cognate to Illyrian Menzanas (as in "Juppiter/Jove Menzanas" 'Juppiter of the foals' or 'Juppiter on a horse');^[38][39][40] Albanian mëz 'foal'; Romanian mînz 'colt, foal';^[41][42] Latin mannus 'small horse, pony';^[43][44] Gaulish manduos 'pony' (as in tribe name Viromandui^[45] 'men who own ponies').^[46][47][b]

Due to a paucity of evidence required to establish a linguistic connection, the Thracian language, in modern linguistic textbooks, is usually treated either as its own branch of Indo-European,^[2] or is grouped with Dacian, together forming a Daco-Thracian branch of IE. Older textbooks often grouped it also with Illyrian or Phrygian. The belief that Thracian was close to Phrygian is no longer popular and has mostly been discarded.^[49]

There is a fringe belief^[50][51] that Thraco-Dacian forms a branch of Indo-European along with Baltic,^[52] but a Balto-Slavic linguistic unity is so overwhelmingly accepted by the Indo-European linguistic community that this hypothesis does not pass muster.

According to the 19th-century Greek educator Vlasios Skordelis, when Thracians were subjugated by Alexander the Great they finally assimilated to Greek culture and became as Greek as Spartans and Athenians, although he considered the Thracian language as a form of Greek.^[53] According to Crampton (1997) most Thracians were eventually Hellenized or Romanized, with the last remnants surviving in remote areas until the 5th century.^[54] According to Marinov (2015) the Thracians were likely completely Romanized and Hellenized after the last contemporary references to them of the 6th century.^[55]

Another author believes that the interior of Thrace was never Romanized or Hellenized (Trever, 1939).^[56] This was followed also by Slavonization. According to Weithmann (1978) when the Slavs migrated, they encountered only a very superficially Romanized Thracian and Dacian population, which had not strongly identified itself with Imperial Rome, while Greek and Roman populations (mostly soldiers, officials, merchants) abandoned the land or were killed.^[57] Because Pulpudeva survived as Plovdiv in Slavic languages, not under Philippopolis, some authors suggest that Thracian was not completely obliterated in the 7th century.^[58][59]

• List of reconstructed Dacian words
• Thraco-Illyrian
• Paeonian language
• Ancient Macedonian language
• Thraco-Roman
• Paleo-Balkan languages
• Proto-Albanian language
• Proto-Balto-Slavic language
• Proto-Greek language