TIGRIS. — One of the two great rivers — the eastern one — that flows from the eastern borders of Asia Minor in a south-easterly direction to the Persian Gulf, forming the "valley of the two rivers" (Mesopotamia [q.v.]), one of the regions where the dawn of human civilization was witnessed.
In its upper course the river, formed by four main branches descending into the southern valleys of the Armenian mountain system (to the west and south of Lake Van), waters several centres, such as Amida and Matarah. The river thus formed flows southwards, with a slight inclination to the east, receiving many tributaries that descend from the Zagros range, such as the Great and Little Zab (Zabac), the 'Adem (Radanu, Φύσχος), and the Diyalah (Turnat, Tornadotus). On its middle course arise some of the greatest centres of antiquity: Nineveh, Kalab (Nimrud), and Assur (Qal'at Serqat). At the height of present-day Baghdad, the Tigris approaches the Euphrates (ca. 50 km.), then, after slightly distancing itself, it once had its own outlet to the sea; even in this stretch it waters important centres such as Upi ('Ομηχ) and Kūt al-'Amarah. Today, however, before reaching the sea the Tigris joins the Euphrates, forming the Shatt al-'Arab, which flows for 50 km. through an alluvial plain where the sea once lay.
In the Bible the Tigris (Heb. Hiddeqel; Sum. Idigna, Akkad. Idiglat, Diglat; Aram. Dighlath, Arab. Dighah; in Old Persian the Aramaic name phonetically became Tigrah, whence the Greek-Latin Τίγρις) is recalled as one of the four rivers of Paradise (Gen. 2:14) and as a river of Mesopotamia it is mentioned in later stories (Dan. 10:4; Tob. 6:1; Jdt. 1:6; Ecclus. 24:25 [24]).
GIOVANNI Rinaldi