Constantine the Great becomes Emperor of Rome, and moves the capital to Byzantium( Constantinople). He also makes Christianity the official religion of the Roman world. 君士坦丁大帝成为罗马皇帝,迁移首都到拜占庭(士坦丁堡)他使天主教成为罗马世界的法定宗教。
byzantium
[ noun ]
an ancient city on the Bosporus founded by the Greeks; site of modern Istanbul; in 330 Constantine I rebuilt the city and called it Constantinople and made it his capital
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a continuation of the Roman Empire in the Middle East after its division in 395
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Byzantium \Byzantium\ prop. n. An ancient city on the Bosphorus founded by the Greeks. It was later renamed {Constaninople} in honor of the emperor Constantine, and renamed {Istanbul} by the Turks, which name it still retains. [WordNet 1.5]