Almost every city developed its own dialect, but the most important dialects we have information on are the "Vegliot" a northern dialect, spoken on the island of Krk ("Veglia" in Italian, "Vikla" in Dalmatian) and the "Ragusan"', a southern dialect, spoken at Dubrovnik ("Ragusa" in both Italian and Dalmatian).
The dialect of Zara disappeared because of the strong Venetian influence while the two other dialects due even to the assimilation by Slavic language speakers.
We know about the dalmatian dialect of Ragusa from two letters, from 1325 and 1397, and other medieval texts, which show a language influenced heavily by Venetian. The available sources include hardly 260 Ragusan words. Surviving words include "pen" (bread), "teta" (father), "chesa" (house) and "fachir" (to do), which were quoted by an Italian, Fillipo Diversi, the head of school of Ragusa in the 1430s.
The "Republic of Ragusa" had at one time an important fleet, but its influence decreased. We know that the language was in trouble in the face of Croatian expansion, as the Ragusan Senate decided that all debates had to be held in "lingua veteri ragusea" (ancient Ragusan language) and the use of the "lingua sclava" (Croatian) was forbidden. Nevertheless, in the 16th century, Ragusan fell out of use and became extinct.
Other languages influenced the Ddalmatian language, but without erasing its Latin roots (superstrates): the Slavs, then the Republic of Venice. Several cities of the regions have Italian names, and other mostly the romanized Illyrian ones (like Zara, Spalato, etc..)
The oldest preserved documents written in Dalmatian are some 13th century inventories, in the Ragusan dialect. A letter of the 14th century from Zara (Zadar) shows strong Venetian influence, which was also the cause of its extinction soon after.
The Christian schism was an important factor in the history of Dalmatia. While the Croatian-held branch of the Catholic Church in Nin was under Pope's jurisdiction, they still used the Slavic liturgy. Both the Latin population of the cities and the Holy See preferred the Latin liturgy, which created tensions between different dioceses.
The great schism between Eastern and Western Christianity of 1054 further intensified the rift between the coastal cities and the hinterland, with many of the Slavs in the hinterland preferring the Eastern Orthodoxy. Areas of today's Bosnia and Herzegovina also had an indigenous "Bosnian Church" which was often mistaken for "Bogomils".
The Latin influence in Dalmatia was increased and the Byzantine practices were further suppressed on the general synods of 1059-1060, 1066, 1075-1076 and on other local synods, notably by demoting the bishopric of Nin, installing the archbishoprics of Spalatum (Split) and Dioclea (Montenegro), and explicitly forbidding use of any liturgy other than Greek or Latin.
Dalmatia never attained a political or racial unity and never formed as a "nation", but it achieved a remarkable development of art, science and literature. Politically, the neolatin Dalmatian city-states were often isolated and compelled to either fall back on the Venetian Republic for support, or tried to make it on their own.
The geographical position of the Dalmatian city states suffices to explain the relatively small influence exercised by Byzantine culture throughout the six centuries (535-1102) during which Dalmatia was part of the Eastern empire. Towards the close of this period Byzantine rule tended more and more to become merely nominal, while the influence of the Republic of Venice increased.
The medieval Dalmatia had still included much of the hinterland covered by the old Roman province of Dalmatia. However, the toponym of "Dalmatia" started to shift more towards including only the coastal, Adriatic areas, rather than the mountains inland. By the 15th century, the word "Herzegovina" would be introduced, marking the shrink of the borders of Dalmatia to the narrow littoral area where was spoken the Dalmatian language (that was being assimilated into the venetian language).
In the thirteenth century the Republic of Venice took definitive control of the Montenegro coast and created the "Albania Veneta".
As the city states gradually lost all protection by Byzantium, being unable to unite in a defensive league hindered by their internal dissensions, they had to turn to either Venice or Hungary for support. Each of the two political factions had support within the Dalmatian city states, based mostly on economic reasons.
The Venetians, to whom the Dalmatians were already bound by language and culture, could afford to concede liberal terms as its main goal was to prevent the development of any dangerous political or commercial competitor on the eastern Adriatic.
The seafaring community in Dalmatia looked to Venice as mistress of the Adriatic. In return for protection, the cities often furnished a contingent to the army or navy of their suzerain, and sometimes paid tribute either in money or in kind. Arbe (Rab), for example, annually paid ten pounds of silk or five pounds of gold to Venice.
Hungary, on the other hand, defeated the last Croat king in 1097 and laid claim on all lands of the Croatian noblemen since the treaty of 1102. King Coloman of Hungary proceeded to conquer Dalmatia in 1102-1105.
The farmers and the merchants who traded in the interior favoured Hungary as their most powerful neighbour on land that affirmed their municipal privileges.
Subject to the royal assent they might elect their own chief magistrate, bishop and judges. Their Roman law remained valid. They were even permitted to conclude separate alliances. No alien, not even a Hungarian, could live in a city where he was unwelcome; and the man who disliked Hungarian dominion could emigrate with all his household and property. In lieu of tribute, the revenue from customs was in some cases shared equally by the king, chief magistrate, bishop and municipality.
These rights and the analogous privileges granted by Venice were, however, too frequently infringed. Hungarian garrisons were being quartered on unwilling towns, while Venice interfered with trade, the appointment of bishops, or the tenure of communal domains. Consequently, the Dalmatians remained loyal only while it suited their interests, and insurrections frequently occurred. Even in Zara four outbreaks are recorded between 1180 and 1345, although Zadar was treated with special consideration by its Venetian masters, who regarded its possession as essential to their maritime ascendancy.
The once rival Romanic and Slavic population eventually started contributing to a common civilization, and Ragusa (Dubrovnik) was the primary example of this. By the 13th century, the councilmen from ragusan names were mixed, and in the 15th century the ragusan literature was even written in the Slavic language (from which Croatian language is directly descended), and the city was often called by its Slavic name, Dubrovnik. Only in 1918 Ragusa was called officially "Dubrovnik", with the creation of Yugoslavia.
The doubtful allegiance of the Dalmatians tended to protract the struggle between Venice and Hungary, which was further complicated by internal discord due largely to the spread of the "Bogomil heresy", and by many outside influences.
The cities of Zara (Zadar), Spalato (Split), Trau (Trogir) and Ragusa (Dubrovnik) and the surrounding territories each changed hands several times between Venice, Hungary and the Byzantium during the 12th century.
In 1202, the armies of the Fourth Crusade rendered assistance to Venice by occupying Zadar for it. In 1204 the same army conquered Byzantium and finally eliminated the Eastern Empire from the list of contenders on Dalmatian territory.