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

Essential Meaning of delta

1 : the fourth letter of the Greek alphabet
2 : a piece of land shaped like a triangle that is formed when a river splits into smaller rivers before it flows into an ocean a river delta the Ganges/Nile Delta
3 US : an area of low land along the Mississippi River that is mainly in the state of Mississippi the Mississippi Delta delta blues [=blues music that comes from the Mississippi delta]

Full 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
2 see delta, the

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Other Words from delta


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

Examples of delta in a Sentence

Recent Examples on the Web: Noun This is the fourth in a series about an eight-month, 10,000-mile road trip around the United States during the rise and fall of the delta variant. Christopher Elliott, Forbes, 9 Oct. 2021 The increase is due to the highly contagious delta variant, relaxed restrictions and ineligibility for children under 12 to get vaccines. Jeanine Santucci, USA TODAY, 9 Oct. 2021 After a summer of rising cases, TGen’s variant tracker shows that the delta variant has become dominant. Melina Walling, The Arizona Republic, 9 Oct. 2021 And last week offered a chance to look back on what the state just endured with the surge fueled by the delta variant, as well as what’s being done to protect workers and schoolchildren as Georgians brace for the cold months ahead. Johnny Edwards, ajc, 9 Oct. 2021 And while there are many reasons to think the delta variant is nearing an end in Alabama, there are still concerns about future variants, Harris and Williamson both said. Ramsey Archibald |, al, 9 Oct. 2021 The delta variant is much more infectious than the previous variants of SARS-CoV-2, the virus that causes COVID-19. Dr. Keith Roach, oregonlive, 8 Oct. 2021 Infection rates among unvaccinated employees have also been 54% higher than vaccinated workers since the delta variant became the region’s dominant coronavirus strain. Ricardo Cano, San Francisco Chronicle, 8 Oct. 2021 The hope was that August was an anomaly but the fact is, the delta variant was still with us in September. NBC News, 8 Oct. 2021 Recent Examples on the Web: Adjective The state had more than 1,100 COVID-19 patients in hospitals at the end of the month, more than double Oregon’s pre-delta peak. oregonlive, 4 Sep. 2021 The United States' delta-variant surge is shifting into a deadly new phase: The number of weekly fatalities is now rising in more than three-quarters of the states. Elinor Aspegren, USA TODAY, 17 Aug. 2021 Of the coronavirus cases that are sequenced at Maryland labs, nearly all are delta variant infections, according to the Maryland Department of Health. Hallie Miller,, 5 Aug. 2021 In non-delta infections from 2020, these tests came out to be positive after six days. Manavi Kapur, Quartz, 27 July 2021 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, 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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Dictionary Entries Near delta



delta agent

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Statistics for delta

Last Updated

12 Oct 2021

Cite this Entry

“Delta.” Dictionary, Merriam-Webster, Accessed 15 Oct. 2021.

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More Definitions for delta


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

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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