Traditionally, Anatolia is considered to extend in the east to an indefinite line running from the Gulf of Alexandretta to the Black Sea, coterminous with the Anatolian Plateau. This traditional geographical definition is used, for example, in the latest edition of "Merriam-Webster's Geographical Dictionary". Under this definition, Anatolia is bounded to the east by the Armenian Highlands, and the Euphrates before that river bends to the southeast to enter Mesopotamia. To the southeast, it is bounded by the ranges that separate it from the Orontes valley in Syria and the Mesopotamian plain.