Sprachbund

During the 3rd millennium BC, a very intimate cultural symbiosis developed between the Sumerians and the Akkadians throughout Mesopotamia, which included widespread bilingualism. The influence of Sumerian (a language isolate) on Akkadian, and vice versa, is evident in all areas, from lexical borrowing on a massive scale, to syntactic, morphological, and phonological convergence. This has prompted scholars to refer to Sumerian and Akkadian in the third millennium BC as a sprachbund. Akkadian gradually replaced Sumerian as the spoken language of Mesopotamia somewhere after the turn of the 3rd and the 2nd millennium BC (the exact dating being a matter of debate), although Sumerian continued to be used as a sacred, ceremonial, literary, and scientific language in Mesopotamia until the 1st century AD, as did the use of the Akkadian cuneiform.