Sumatra(1), the world's fifth largest island, is located southwest of the Malay Peninsula, northwest of Java(2) and west of Borneo(3). It stretches northwest to southeast with archipelagoes of small islands off its southeast, west, and northwest. A mountain range flanks the west. In the north these highlands are uninhabited despite the nearly 40 million islanders elsewhere. The southeast is flat and marshy with rivers flowing eastward from the mountains.
Everyone(4) speaks Austronesisan languages, but byeond that generalization is great diversity. I. The most important language is Malay(5), spoken by just under half as a first language, but--as the national tongue and an old lingua franca--learned by most, of the island's residents. It is spoken in many areas west of the mountains, especially in the south. II. The next most important language is a close relative, Minangkabau, spoken as a first language by almost one in four. It is spoken in the west center. (Malay and Minangkabau are in the Malayan group, which accounts for more than three-fourths of the island's speakers.) III. Aceh is the third most important, with one in nine speakers, all in Aceh Province. IV. Batak proper is spoken by only seven percent of speakers, but the seven closely related Batak languages account for more than one in five islanders. These languages are spoken just south of Aceh. V. Lampung is spoken by about six percent, all in the south. VI. Recent migrants, huge in number in southern Sumatra, have introduced Javanese.
The majority--more than eight in ten--is Sunni Moslem. More than one in ten are Christians, notably the Bataks who are Lutheran Christians; some of these practice a syncretic mixture of Christianity, Islam and animism. There are an uncertain number included in the statistics of belivers who are secretly communist aetheists.
The island's principle cities are Medan and Palembang. The first, on the Deli River in the north, administers Belawan, the nation's chief port, handling 65 percent of its exports. The second is in the southeast and was the capital of the Srivijaya Empire. Today it is an oil refining center and port.
According to lingusitic theory, Austronesian languages arrived from the north 30,000 years ago, ultimately from Taiwan via the Philippines. There have been inhabitants here for many more tens of thousands of years, but nothing is known of their languages. Aceh is related to Cham, a language and former state in Indo-China. Malay is the regional lingua franca. It originated in three places: Riau Province, Sumatra; across the straits in Malaysia; and in southwest Borneo. Its growth continues particularly in southern Sumatra.
Buddhism began in southern Sumatra in the seventh century and, under the political power of the Srivijaya Empire, long dominated the island. In the 13th century Islam arrived in the north and slowly gained adherants. By the early 16th century the east coast was Moslem-ruled down to Palembang, but Moslems were scarcer in the west. In subsequent centuries Islam became ubiquitous. Christianity arrived with Dutch colonization, but conversion was limited to marginal groups.
Around Sumatra and close-by island groups:
north of the Andaman Islands
east of the Andaman and Nicobar Islands and north of Sumatra
northeast of Sumatra
north of the Riau Islands
east of the Riau Islands, and north of the islands of Bangka and Belitung
northeast of Belitung Island
east of southern Sumatra, and southeast of the islands of Bangka and Belitung
southeast of Sumatra
southwest of Sumatra
west of the Andaman and Nicobar Islands
Around the Anambas and Natuna Islands:
north
southeast
south and southwest
(1) Sumatera in Malay-Indonesian.
(2) Jawa in Malay-Indonesian.
(3) Kalimantan in Malay-Indonesian.
(4) Except on the Andaman and Nicobar Islands.
(5) Called Indonesian within Indonesia.