General English

  • noun a triangular piece of land at the mouth of a large river, formed of silt carried by the river


  • The fourth letter of the greek alphabet, and as such may designate the fourth constituent of a series.
  • A net change in the value of a variable.
  • Having the shape of its symbol, or that of a triangle. Said, for instance, of a circuit.

Media Studies

  • noun
    (written as Delta)
    an internationally recognised code word for the letter D, used in radio communications


  • noun a triangular area of land or marsh at the mouth of a river
  • noun
    (written as Delta)
    the fourth letter of the phonetic alphabet (Dd)

Origin & History of “delta”

Delta was the fourth letter of the Greek alphabet, corresponding to English d. Its capital form was written in the shape of a tall triangle, and already in the ancient world the word was being applied metaphorically to the triangular deposit of sand, mud, etc which forms at the mouth of rivers (the Greek historian Herodotus, for instance, used it with reference to the mouth of the Nile). Greek acquired the word itself from some Semitic language; it is related to dāleth, the name of the fourth letter of the Hebrew alphabet.