delta

/del"teuh/, n.

1. the fourth letter of the Greek alphabet.

2. the consonant sound represented by this letter.

3. the fourth in a series of items.

4. anything triangular, like the Greek capital delta.

5. Math. an incremental change in a variable.

6. a nearly flat plain of alluvial deposit between diverging branches of the mouth of a river, often, though not necessarily, triangular: the Nile delta.

7. (usually cap.) a word used in communications to represent the letter D.

8. (cap.) Astron. a star that is usually the fourth brightest of a constellation: The fourth brightest star in the Southern Cross is Delta Crucis.

[1350-1400; ME deltha < L delta < Gk délta; akin to Heb daleth]

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Low-lying plain composed of stream-borne sediments deposited by a river at its mouth.

Deltas have been important to humankind since prehistoric times. Sands, silts, and clays deposited by floodwaters were extremely productive agriculturally; and major civilizations flourished in the deltaic plains of the Nile and Tigris-Euphrates rivers. In recent years geologists have discovered that much of the world's petroleum resources are found in ancient deltaic rocks. Deltas vary widely in size, structure, composition, and origin, though many are triangular (the shape of the Greek letter delta).

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▪ British Columbia, Canada

      district municipality, southwestern British Columbia, Canada. It is situated in the southern Vancouver metropolitan area, between the Fraser River delta and Boundary Bay (an arm of the Strait of Georgia). Though its northern section is primarily residential, much of its area is devoted to dairying, truck gardening, and farming cash crops. Delta's industries, which are mainly concentrated on Annacis Island in the Fraser River, include fishing and fish canning, food processing, and paper milling. Robert Bank, a superport built for the bulk handling of coal and completed in 1970, occupies a 55-acre (22-hectare) man-made island in the Strait of Georgia off the suburb's western shore. Delta has several fine beaches and ferry service to Vancouver Island. Inc. 1879. Pop. (2006) 96,723.

▪ Utah, United States

      city, Millard county, west-central Utah, U.S. Delta is one of the few Utah towns to have been founded in the 20th century with little involvement from the Mormon church, which tightly controlled settlement in the region. Originally an agricultural cooperative called Melville, founded in 1906, the community was reorganized in 1911 and renamed Delta by the Delta Land and Management Company (investment firm). At first a centre of sugar beet production, Delta developed a diversified agricultural economy and became a leading producer of alfalfa in the 1920s. Fluorspar mining and electricity production contributes to the local economy, as does tourism. The Great Basin Historical Society Museum was opened in 1989 and is an important local attraction. On the museum's grounds stands a restored barracks from the Topaz Relocation Center, used during World War II to confine Japanese Americans from the San Francisco area. Inc. 1911. Pop. (1990) 2,998; (2000) 3,209.

▪ launch vehicle

 American three-stage space-launch vehicle; its development began in 1959. The first version was capable of placing a 480-pound (220-kilogram) payload into a 300-mile (480-kilometre) orbit. In the early 1960s, Delta launched TIROS weather satellites, Echo 1, and the Telstar, Relay, and Syncom communication satellites. An improved Delta with a more powerful first stage and capable of placing 1,000 pounds (450 kg) into a 500-mile (800-kilometre) orbit put the Syncom 3 communication satellite into orbit on Aug. 19, 1964. Several Long Tank Deltas were also built; an advanced version has an inertial guidance system and can be flown with either two or three stages. The two-stage version is capable of placing a 3,600-pound (1,630-kilogram) payload into a 230-mile (370-kilometre) orbit.

▪ state, Nigeria

      state, southern Nigeria. It is bounded by Edo state to the north, Anambra state to the east, Rivers state to the southeast, Bayelsa state to the south, the Bight of Benin (Benin, Bight of) of the Atlantic Ocean to the west, and Ondo state to the northwest. On the east and south the state is bounded by the lower course and delta of the Niger River. Delta was created in 1991 from the southern half of former Bendel state. Asaba, on the Niger River, is the state capital.

      Most of the state lies at an elevation below 500 feet (150 metres) in the Niger River delta. Mangrove swamps predominate in the delta and merge with freshwater swamps to the north. A maze of interconnected waterways and the Forcados (Forcados River) and Escravos (Escravos River) rivers, which empty into the Bight of Benin, are used for transportation. The state is inhabited by the Igbo people in the east, the Edo in the north, and the Itsekiri, Urhobo, Isoko, and Ijo in the south and west.

      Agriculture is the mainstay of the state's economy; yams, cassava (manioc), oil palm produce, rice, and corn (maize) are grown for local consumption. Delta is a major exporter of petroleum, rubber, timber, and palm oil and palm kernels via the Niger delta ports of Burutu, Forcados, Koko, Sapele, and Warri. Petroleum is exported by pipeline from the Ughelli fields, and other major oil fields exist near Warri (which possesses an oil refinery), Koko, and Escravos, as well as offshore. The state's industries include glass and bottle factories, textile mills, and plastics, rubber, plywood, natural gas, boatbuilding, sawmilling, and furniture industries. A major steel-producing complex is at Aladja, adjacent to Warri. A bridge crosses the Niger from Asaba to Onitsha. Area 6,833 square miles (17,698 square km). Pop. (2006) 4,098,391.

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