Rûm (Arabic pronunciation: ['ru:m?]; singular Rûmi), also transliterated as Roum (in Arabic ar-R?m; in Persian and Ottoman Turkish Rûm; in Turkish: Rum), is a derivative of the term ? (Rhomaioi). The latter was an endonym of the (pre-Islamic) inhabitants of Turkey, the Middle East, and the Balkans, dating to when those regions were parts of the Eastern Roman (Byzantine) Empire.
The term Rûm is now used to describe:
Rûm is found in the pre-Islamic Namara inscription and later in the Quran (7th century), where it refers to a contemporary ruler (Heraclius) of the Eastern Roman (Byzantine) Empire, the Western Roman Empire having fallen two centuries earlier (5th century).
The Qur'an includes the Surat Ar-Rum (the sura dealing with "the Romans", sometimes translated as "The Byzantines"). These people, referred to as Byzantines in modern Western scholarship, were inhabitants of the Eastern Roman (Byzantine) Empire and called themselves or ? Rhomaioi Romans in their own language. (The term "Byzantine" is a modern designation to describe the Eastern Roman Empire, particularly after the major political restructuring of the seventh and eighth century.) The city of Rome was known in classical Arabic instead as R?miyah (in modern Arabic as R?m? ?), and Ancient Romans were called instead "R?m" or sometimes "Latin'yun" (Latins). The Arabs called Ancient Greece by the name "Y?n?n" (Ionia) and ancient Greeks "Y?n?n?m" (similar to Hebrew "Yavan" [?] for the country and "Yevanim"  for the people). The Byzantine state shrank from encompassing the eastern Mediterranean in 395 AD to consisting only of what is now modern Turkey and the Balkans in 700 AD; it finally fell in 1453 AD. The Arabs, therefore, called these pre-Islamic peoples of Turkey, the Balkans, and the Middle East "Rûm", and called their territory "the land of the Rûm", generally referring to what is now Turkey and the Balkans, and called the Mediterranean "the Sea of the Rûm". After the fall of the Byzantine state in the 15th century, the Ottoman sultan Mehmed II declared himself Kayser-i Rum, literally "Caesar of the Romans". In the Ottoman Millet system, the Eastern Orthodox subject peoples (i.e. the conquered Byzantines) were placed into the "Rum Millet" (Millet-i Rum). In modern Turkey, Rum is still used to denote the Greek Orthodox minority population of Turkey and other pre-conquest remnants, cf. Rum Ortodoks Patrikhanesi, the Turkish designation of the Ecumenical Patriarchate of Constantinople in Istanbul.
Because Muslim contact with the Byzantine Empire most often took place in Asia Minor, which was the heartland of the Byzantine state from the seventh century onward, the term Rûm became fixed there geographically. The term remained even after the conquest of central Asia Minor by the Seljuk Turks, so their territory was called the land of the Seljuks of Rûm or the Sultanate of Rûm.
Al-R?m? is a nisbah designating people originating in the Byzantine Roman Empire or lands that formerly belonged to Byzantine Roman Empire, especially Anatolia. Historical people so designated include the following:
The term "Urums", also derived from the same origin, is still used in contemporary ethnography to denote Turkic-speaking Greek populations. "Rumeika" is a Greek dialect identified mainly with the Ottoman Greeks.
Chinese, during the Ming dynasty, referred to the Ottomans as Lumi (), derived from Rum or Rumi. The Chinese also referred to Rum as Wulumu during the Qing dynasty. The modern Mandarin Chinese name for the city of Rome is Luoma ().