The regional toponym Mesopotamia (/, Ancient Greek: Μεσοποταμία "[land] between rivers"; Arabic: بلاد الرافدين، بین النهرین bilād ar-rāfidayn; Persian: میانرودان miyān rudān; Syriac: ܒܝܬ ܢܗܪܝܢ Beth Nahrain "land of rivers") comes from the ancient Greek root words μέσος (mesos) "middle" and ποταμός (potamos) "river" and translates to "(Land) between two/the rivers". It is used throughout the Greek Septuagint (c. 250 BC) to translate the Hebrew and Aramaic equivalent Naharaim. An even earlier Greek usage of the name Mesopotamia is evident from The Anabasis of Alexander, which was written in the late 2nd century AD, but specifically refers to sources from the time of Alexander the Great. In the Anabasis, Mesopotamia was used to designate the land east of the Euphrates in north Syria.
The Aramaic term biritum/birit narim corresponded to a similar geographical concept. Later, the term Mesopotamia was more generally applied to all the lands between the Euphrates and the Tigris, thereby incorporating not only parts of Syria but also almost all of Iraq and southeastern Turkey. The neighbouring steppes to the west of the Euphrates and the western part of the Zagros Mountains are also often included under the wider term Mesopotamia.
A further distinction is usually made between Northern or Upper Mesopotamia and Southern or Lower Mesopotamia. Upper Mesopotamia, also known as the Jazira, is the area between the Euphrates and the Tigris from their sources down to Baghdad. Lower Mesopotamia is the area from Baghdad to the Persian Gulf and includes Kuwait and parts of western Iran.
In modern academic usage, the term Mesopotamia often also has a chronological connotation. It is usually used to designate the area until the Muslim conquests, with names like Syria, Jazira, and Iraq being used to describe the region after that date. It has been argued that these later euphemisms are Eurocentric terms attributed to the region in the midst of various 19th-century Western encroachments.