structural:summarization, linguistic:paraphrasing
Late antiquity (4th to 6th centuries AD)

The Roman Empire began to weaken as a result of the crisis of the third century. During Late antiquity Christianity became increasingly popular, finally ousting the Roman imperial cult with the Theodosian decrees of 393. Successive invasions of Germanic tribes finalized the weakening of the Western Roman Empire during the 5th century, while the Eastern Roman Empire persisted throughout the Middle Ages, in a state called Romania by its citizens, and designated the Byzantine Empire by later historians. Hellenistic philosophy was succeeded by continued development of Platonism and Epicureanism, with Neoplatonism in due course influencing the theology of the Christian Church Fathers.

Many writers have attempted to name a specific date for the symbolic "end" of antiquity, with the most prominent dates being the deposing of the last Western Roman Emperor in 476, the closing of the last Platonic Academy in Athens by the Eastern Roman emperor Justinian I in 529, and the conquest of much of the Mediterranean by the new Muslim faith from 634 to 718. These Muslim conquests, of Syria (637), Egypt (639), Cyprus (654), North Africa (665), Hispania (718), Southern Gaul (720), Crete (820), and Sicily (827), Malta (870), as well as the sieges of the Eastern Roman capital (first in 674–78 and then in 717–18) severed the economic, cultural, and political links that had traditionally united the classical cultures around the Mediterranean, ending antiquity (see Pirenne Thesis).

The original Roman Senate continued to express decrees into the late 6th century, and the last Eastern Roman emperor to use Latin as the language of his court in Constantinople was emperor Maurice, who reigned until 602. The overthrow of Maurice by his mutinying Danube army commanded by Phocas resulted in the Slavic invasion of the Balkans and the weakening of Balkan and Greek urban culture (resulting in the flight of Balkan Latin speakers to the mountains, see Origin of the Romanians), and also provoked the Byzantine–Sasanian War of 602–628 in which all the great eastern cities except Constantinople were lost. The resulting turmoil did not end until the Muslim conquests of the 7th century finalized the irreversible loss of all the largest Eastern Roman imperial cities besides the capital itself. The emperor Heraclius in Constantinople, who reigned during this period, conducted his court in Greek, not Latin, though Greek had always been an administrative language of the eastern Roman regions. Eastern-Western associations weakened with the ending of the Byzantine Papacy.

The Eastern Roman empire's capital city Constantinople remained the only unconquered large urban site of the original Roman empire, as well as being the largest city in Europe. Yet many classical books, sculptures, and technologies survived there along with classical Roman cuisine and scholarly traditions, well into the Middle Ages, when much of it was "rediscovered" by visiting Western crusaders. Indeed, the inhabitants of Constantinople continued to refer to themselves as Romans, as did their eventual conquerors in 1453, the Ottomans (see Romaioi and Rûm.) The classical scholarship and culture that was still preserved in Constantinople were brought by refugees fleeing its conquest in 1453 and helped to begin the Renaissance (see Greek scholars in the Renaissance).

Ultimately, it was a slow, complex, and graduated change of the socio-economic structure in European history that resulted in the changeover between classical antiquity and medieval society and no specific date can truly exemplify that.