In the 10th century the features of the modern dialects were already fully formed, while the prestige of the 'koine', the official language, gradually lessened, as large parts of the Byzantine state came under Frankish control.
As a result, many loan-words were introduced from Italian (mainly in the vocabulary of arts and crafts, and that of navigation) and French (mainly in the vocabulary of feudal law and land-tenure). At the same time, the spoken form of the language was used in writing more widely than before.
The fact that the surviving texts do not show prominent dialectal features suggests that a common language was created; this spoken form of the language existed in parallel with the local dialects and was used in the large urban centres of Byzantium -- among them Thessalonike and Serrhai -- by the constantly moving merchants, administrators and military officials.
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