[ del-tuh ]
See synonyms for delta on
  1. the fourth letter of the Greek alphabet (Δ, δ).

  2. the consonant sound represented by this letter.

  1. the fourth in a series of items.

  2. anything triangular, like the Greek capital delta (Δ).

  3. Mathematics. an incremental change in a variable, as Δ or δ.

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

  5. Also Delta . a word used in communications to represent the letter D.

  6. Delta, Astronomy. a star that is usually the fourth brightest of a constellation: The fourth brightest star in the Southern Cross is Delta Crucis.

Origin of delta

First recorded in 1150–1200; Middle English delta, deltha, from Latin delta, from Greek délta; akin to Hebrew dāleth

Words that may be confused with delta

Other definitions for Delta (2 of 2)

[ del-tuh ]

  1. the NATO name for a class of nuclear-powered submarines armed with multiple-warhead ballistic missiles, including those designed to strike military and industrial installations: first produced for the Soviet Navy in the 1970s; in service with the Russian Navy since 1992. Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use delta in a sentence

  • The broad plains formed at the mouth of a river are called deltas, from their resemblance to the Greek letter Δ.

    Geology | James Geikie
  • The term delta, however, is not exclusively applied to fluvio-marine deposits; rivers also form deltas in fresh-water lakes.

    Geology | James Geikie
  • The Meuse and the Rhine form numerous mouths, and their deltas are low and marshy.

    The Youthful Wanderer | George H. Heffner
  • The deltas of the great rivers afford corroboration to our position as to man's duration.

    A Few Words About the Devil | Charles Bradlaugh
  • Deltas are also formed where streams lose their velocity on entering the still waters of lakes.

    The Elements of Geology | William Harmon Norton

British Dictionary definitions for delta (1 of 3)


/ (ˈdɛltə) /

  1. the fourth letter in the Greek alphabet (Δ, δ), a consonant transliterated as d

  2. an object resembling a capital delta in shape

  1. (capital when part of name) the flat alluvial area at the mouth of some rivers where the mainstream splits up into several distributaries: the Mississippi Delta

  2. maths a finite increment in a variable

Origin of delta

C16: via Latin from Greek, of Semitic origin; compare Hebrew dāleth

Derived forms of delta

  • deltaic (dɛlˈteɪɪk) or deltic, adjective

British Dictionary definitions for Delta (2 of 3)


/ (ˈdɛltə) /

  1. (foll by the genitive case of a specified constellation) usually the fourth brightest star in a constellation

  2. any of a group of US launch vehicles used to put unmanned satellites into orbit

  1. communications a code word for the letter d

British Dictionary definitions for Delta (3 of 3)


/ (ˈdɛltə) /

  1. a state of Nigeria, on the Niger river delta on the Gulf of Guinea. Capital: Asaba. Pop: 4 098 391 (2006). Area: 17 698 sq km (6833 sq miles)

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Scientific definitions for delta


[ dĕl ]

  1. A usually triangular mass of sediment, especially silt and sand, deposited at the mouth of a river. Deltas form when a river flows into a body of standing water, such as a sea or lake, and deposits large quantities of sediment. They are usually crossed by numerous streams and channels and have exposed as well as submerged areas.

The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.