Main definitions of delta in English

: delta1delta2

delta1

noun

  • 1The fourth letter of the Greek alphabet (Δ, δ), transliterated as ‘d’.

    • ‘Other symbols use in chemistry include the Greek letter delta to denote a change in energy levels and an arrow to indicate the direction a reaction proceeds in.’
    • ‘It should be noted that the scaled necrosis depth, d / delta, also depends on the irradiation geometry and the incident light dose.’
    • ‘Apparently they don't teach you anything useful, just epsilons and deltas.’
    • ‘Casey guessed the next would be delta: phonetic alphabet’
    1. 1.1British A fourth-class mark given for an essay, examination paper, or other piece of work.
    2. 1.2[as modifier] The fourth in a series of items, categories, etc.:
      ‘delta hepatitis’
      • ‘Our results suggest that delta infection may not be very common in Indian patients with HBV-related liver diseases.’
      • ‘Thus, our results suggest that delta co-infection is more common in acute liver diseases while delta super-infection occurs more frequently in chronic liver disease.’
      • ‘For example, the babies are taught to be satisfied with their own caste of which there are five: alphas at the top, then betas, gammas, deltas, and epsilons at the bottom.’
      • ‘To me it looked like the alpha males on the rampage, and alpha males are always scary to all the gamma and delta males.’
      • ‘The study reports the influence of delta infection on the severity of hepatitis B.’
      • ‘Four changes occur in iron, which give rise to forms known as alpha, beta, gamma and delta.’
    3. 1.3Astronomy [followed by Latin genitive] The fourth (usually fourth-brightest) star in a constellation:
      ‘Delta Cephei’
      • ‘As a connecting star to Pegasus, it is also known as Delta Pegasi, though this name is rarely used.’
      • ‘Other bright stars in Canis Major are Adhara (Epsilon Canis Majoris), Mirzam (Beta Canis Majoris), and Wezen (Delta Canis Majoris).’
  • 2A code word representing the letter D, used in radio communication.

    • ‘Pilot: Regina Tower, (this is) Cessna foxtrot bravo charlie delta (over).’

  • 1Mathematics
    Variation of a variable or function.

  • 2Mathematics
    A finite increment.

  • 3Astronomy
    Declination.

Origin

Greek, from Phoenician daleth.

Pronunciation:

delta

/ˈdɛltə/

Main definitions of delta in English

: delta1delta2

delta2

noun

  • A triangular tract of sediment deposited at the mouth of a river, typically where it diverges into several outlets:

    ‘the Nile delta’
    [as modifier] ‘a huge delta system developed’
    • ‘These lead down to what appears to be a shoreline with river deltas and sand bars.’
    • ‘They carry silt from the Mississippi River that replenishes the delta and keeps the coastland above the water line, creating a gradual buffer from the sea.’
    • ‘Irrigated rice agriculture is also practiced in numerous smaller river deltas and plains along the country's coast.’
    • ‘Discriminating between deposits of tidally influenced deltas and tide-dominated coastal mud flats in the rock record is often difficult.’
    • ‘Erpetoichthys calabaricus is distributed solely in tropical Africa, where it occupies habitats ranging from flowing rivers to flood plains and internal river deltas.’
    • ‘Long and narrow it stretches east to west along the Gambia River and the capital, Banjul, lies on an island in the river delta.’
    • ‘In time, as the Ecca Sea filled with sediment and the deltas prograded basinward, large tracts of river channels and floodplains emerged.’
    • ‘The forests and estuaries of the delta also benefited from huge floods released into the river from behind dams during the El Niño years of the 1980s and 1990s.’
    • ‘You can't save beaches and wetlands with seawalls, and you can't wall off river deltas and floodplains that contain much of the world's most productive agricultural land.’
    • ‘But those levees denied the delta replenishing river sediment, just as oil prospectors began to dredge coastal wetlands.’
    • ‘The flows lead down to a shoreline which scientists think has river deltas and sandbars, all familiar geographical features from home.’
    • ‘Most Pamiri villages exist at the triangle of a river delta.’
    • ‘Water flow in the rivers decreased when the region's climate changed about 5,000 years ago and wind began to winnow the river delta's dried sediments.’
    • ‘As the rate of rising sea level gradually slowed, rivers began to build deltas from retreating shorelines into the encroaching seas.’
    • ‘In Bangladesh, settlement of populations in high risk areas such as floodplains and river deltas increases vulnerability.’
    • ‘Innumerable lagoons, lakes, canals, estuaries and the deltas of 44 rivers make up the 900 km of backwater network of the State.’
    • ‘The minerals are deposited in lakes, deltas and meander further downstream, where they build up and form sedimentary rocks such as calcite, selenite, pyrite and dolomite.’
    • ‘It and many other old zircons come from metamorphosed sediments deposited in river deltas some 3 billion years ago in what is now southwestern Australia.’
    • ‘Here in northern Idaho, near where the deluge began, I survey the rounded mountains and river deltas, trying to imagine the force of such a catastrophe.’
    • ‘The Teshekpuk area, a network of wet meadows, river deltas, coastal lagoons and small ponds, is the prime calving grounds for a 25,000-strong caribou herd.’

Origin

Mid 16th century: originally specifically as the Delta (of the River Nile), from the shape of the Greek letter (see delta).

Pronunciation:

delta

/ˈdɛltə/