Later Thracians became more or less civilized under the Greek influence, and even established their own kingdom in southern Bulgaria in the 5th century BC. Some Thracians migrated into Asia Minor and established there a kingdom named Viphynia. Then Thrace became successively a Macedonian, Roman, and Byzantine province. By the fall of Constantinople (present-day Istanbul) in 1453, Thrace came under the control of the Ottoman Empire. At that time, no one remembered the Thracian language, because these lands were inhabited already by Slavic peoples, migrants from the North, who together with Romans, Byzantine Greeks, Bulgars and Hungarians assimilated original Thracian tribes.
The language was for sure Indo-European, though too little is known about it. It had three or more cases, highly inflected nouns and verbs, and lexical system similar to Proto-Indo-European and also related to Greek and Phrygian. Many words from Thracian are easily recognized by Slavic or Romance speakers. This fact is evident, although the Thracian glossary consists of few words, mainly of toponymic terms, names of towns and special plants. The nouns, obviously, had two genders. That's all we know, but the source of studies is still very wide.
Some signs of Thracian language are preserved in Rumanian (which in
fact is a mixture of Latin and Thracian) and Bulgarian. Several words