That portion of Babylonia which lay south and east of Babylon, though the name was sometimes used after the days of Jeremiah to denote the whole district lying between and adjoining the rivers Tigris and Euphrates. The Chaldeans (using the word in its wider sense) belonged to the same race as the Assyrians and spoke the same language. In Dan. 2: 2, 10 the name is applied to a learned class in Babylon who made a special study of astrology.