Photo Courtesy of NASA
Asia is the central and eastern part of Eurasia, and the world's largest continent. Defined by subtracting Europe from Eurasia, Asia is either regarded as a landmass of its own, or as part of Eurasia.
The demarcation between Asia and Africa is the isthmus of Suez (although the Sinai Peninsula, being a part of Egypt east of the canal, is often geopolitically considered a part of Africa). The boundary between Asia and Europe runs via the Dardanelles, the Sea of Marmara, the Bosporus, to the Black Sea, the Caucasus Mountains, the Caspian Sea, the Ural River to its source, and the Ural Mountains to the Kara Sea at Kara, Russia. About 60 percent of the world's human population lives in Asia.
Asia as a political division consists of the eastern part of Eurasia and nearby islands in the Indian and Pacific Oceans, often excluding Russia.
The word Asia entered English, via Latin, from Ancient Greek. This name is first attested in Herodotus (c. 440 BC), where it refers to Asia Minor; or, for the purposes of describing the Persian Wars, to the Persian Empire, as opposed to Greece and Egypt. Even before Herodotus, Homer knew of a Trojan ally named Asios, son of Hyrtacus, a ruler over several towns, and elsewhere he describes a marsh. The Greek term may be derived from from Assuwa, a 14th century BC confederation of states in Western Anatolia. Hittite assu- "good" is probably an element in that name.
Alternatively, the ultimate etymology of the term may be from the Akkadian word which means "to go out", referring to the direction of the sun at sunset in the Middle East. This may be compared to a similar etymology proposed for Europe, as being from Semitic erēbu "to enter" or "set" (of the sun). These etymologies presuppose an originally Mesopotamian or Middle Eastern perspective, which would explain how the term "Asia" first came to be associated with Anatolia as lying west of the Semitic speaking area.
The mean elevation of the continent is 950 m (3,117 ft.), the largest of any in the world. The plateau and mountainous areas broadly sweep SW-NW across Asia, climaxing in the high Tibetan Plateau, rising to the highest peaks in the world in the Himalaya. To the north west lie plains, while to the south lie the geologically distinct areas of the Arabian peninsula, Indian subcontinent and Malay peninsula. Large numbers of islands lie south east of the continent.