del·​ta | \ ˈdel-tə How to pronounce delta (audio) \

Definition of delta

 (Entry 1 of 5)

1 : the 4th letter of the Greek alphabet — see Alphabet Table
2 : something shaped like a capital Greek delta especially, geology : the alluvial deposit at the mouth of a river the Mississippi Delta
3 mathematics : an increment of a variable symbol Δ

Definition of delta (Entry 2 of 5)

: fourth in position in the structure of an organic (see organic entry 1 sense 1b(2)) molecule from a particular group or atom symbol ƍ


communications code word

Definition of Delta (Entry 3 of 5)

used as a code word for the letter d

Definition of Delta (Entry 4 of 5)

: of, relating to, or characteristic of the The Delta region of Mississippi


geographical name
Del·​ta | \ ˈdel-tə How to pronounce Delta (audio) \

Definition of Delta (Entry 5 of 5)

1 municipality south and southeast of Vancouver in southwestern British Columbia, Canada population 99,863

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Other Words from delta


deltaic \ del-​ˈtā-​ik How to pronounce deltaic (audio) \ adjective

Examples of delta in a Sentence

Recent Examples on the Web: Noun A century ago, the Army Corps of Engineers built levees around the Mississippi River, limiting the delta’s ability to constantly rebuild itself through the ebb and flow of sediment-carrying water. Eric Roston,, "‘Nothing Left’: How Back-to-Back Hurricanes Gutted a U.S. Town," 11 Oct. 2020 In the second of our Delta on the Edge series, reporter Kurtis Alexander explains how Willson is trying to renovate the cruise ship and how the barriers in his way reflect a changing delta. Taylor Kate Brown,, "Bay Briefing: They’re still sheltering in place, seven months later," 9 Oct. 2020 If a call has a delta of 0.50 and the price of the underlying stock rises $1, the price of the call will go up, theoretically, about 50 cents, as long as everything else remains constant. Nick Ravo, WSJ, "These Options Terms Are Greek to You," 5 Oct. 2020 Other commissions include a 23-foot-wide water lily designed by de Kock and sculpted by South African Otto du Plessis that will reflect the dark delta waters flowing beneath the property’s elevated walkways. Travis Levius, Travel + Leisure, "This New Safari Lodge Is Like an African Art Gallery in the Wild," 4 Oct. 2020 Keleher and Lawrence hope the delta restoration will put the fish on a path to long-term survival without assistance. Brian Maffly, The Salt Lake Tribune, "A little reservoir behind the University of Utah is helping save an endangered fish," 26 Sep. 2020 The researchers took that delta—the difference in case rates between each county and its control—and multiplied it by the total cases each county had accumulated before the rally. Megan Molteni, Wired, "How Much Do Crowds Contribute to Covid? It's Complicated," 11 Sep. 2020 The island itself is near the outermost edge of the Mississippi delta, where the land fragments and dissolves into the Gulf of Mexico. Tim Mcdonnell, Quartz, "Louisiana’s population is already moving to escape climate catastrophe," 1 Sep. 2020 In the heart of the oil-rich delta in southeastern Nigeria, darkness never falls. Somini Sengupta New York Times, Star Tribune, "Inequality at the boiling point: Extreme heat takes toll on poor, vulnerable," 20 Aug. 2020 Recent Examples on the Web: Adjective Fisheries experts and environmentalists say the tunnels will devastate delta fish by depriving them of the most critical ingredient in their survival — freshwater. Peter Fimrite, San Francisco Chronicle, "California’s two-tunnel Delta project is back on track with SoCal water district’s vote," 10 Apr. 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'delta.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of delta


13th century, in the meaning defined at sense 1

Adjective (1)

circa 1929, in the meaning defined above

Communications code word

1952, in the meaning defined above

Adjective (2)

1859, in the meaning defined above

History and Etymology for delta

Noun and Adjective (1)

Middle English deltha, from Greek delta, of Semitic origin; akin to Hebrew dāleth daleth

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Time Traveler for delta

Time Traveler

The first known use of delta was in the 13th century

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Statistics for delta

Last Updated

23 Oct 2020

Cite this Entry

“Delta.” Dictionary, Merriam-Webster, Accessed 29 Oct. 2020.

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More Definitions for delta


How to pronounce Delta (audio)

English Language Learners Definition of delta

: the fourth letter of the Greek alphabet
: a piece of land shaped like a triangle that is formed when a river splits into smaller rivers before it flows into an ocean
US : an area of low land along the Mississippi River that is mainly in the state of Mississippi


del·​ta | \ ˈdel-tə How to pronounce delta (audio) \

Kids Definition of delta

: a piece of land in the shape of a triangle or fan made by deposits of mud and sand at the mouth of a river


del·​ta | \ ˈdel-tə How to pronounce delta (audio) \

Medical Definition of delta

 (Entry 1 of 2)

1 : the fourth letter of the Greek alphabet symbol Δ or ƍ
2 : any of various things felt to resemble a capital Δ especially : the triangular terminus of a pattern in a fingerprint formed either by bifurcation of a ridge or by divergence of two ridges that are parallel beyond it


variants: or ƍ-

Medical Definition of delta (Entry 2 of 2)

1 : of or relating to one of four or more closely related chemical substances the delta chain of fetal hemoglobin ƍ-yohimbine used somewhat arbitrarily to specify ordinal relationship or a particular physical form and especially one that is allotropic, isomeric, or stereoisomeric (as in ƍ-benzene hexachloride)
2 : fourth in position in the structure of an organic molecule from a particular group or atom also : having a structure characterized by such a position ƍ-hydroxy acids ƍ-lactones

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More from Merriam-Webster on delta

Nglish: Translation of delta for Spanish Speakers

Britannica English: Translation of delta for Arabic Speakers Encyclopedia article about delta

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