delta

1 of 4

noun

del·​ta ˈdel-tə How to pronounce delta (audio)
plural deltas
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
4
: delta wave
During deep sleep, the brain operates in delta wave frequency. But it's difficult to go from beta to theta then delta without first switching down to a relaxed alpha state.Daily Mail (London)
5
or less commonly Delta : delta variant
As SARS-CoV-2 continues to spread among humans, natural selection and adaptation will result in more variants that could plausibly be more transmissible than delta.Suresh V. Kuchipudi
deltaic adjective

delta

2 of 4

adjective (1)

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

Delta

3 of 4

communications code word

used as a code word for the letter d

Delta

4 of 4

adjective (2)

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

Example Sentences

Recent Examples on the Web
Noun
The specimens in question come from the Mazon Creek fossil deposits of Northern Illinois, an ancient delta that preserved millions of soft-bodied organisms when they were buried rapidly in muddy sediments. Tim Newcomb, Popular Mechanics, 8 Mar. 2023 Newsom, for example, is trying to waive environmental rules aimed at keeping juvenile salmon alive in the delta. Los Angeles Times, 20 Feb. 2023 The depot is near the base of an ancient river delta that once flowed into Jezero Lake. Sarah Kuta, Smithsonian Magazine, 1 Feb. 2023 And the landing was a success, placing the rover at the edge of a structure that appeared to be a river delta where the nearby highlands drained into the crater. John Timmer, Ars Technica, 23 Nov. 2022 The city of Antioch has shown as much initiative as any Bay Area supplier, recently breaking ground on a small desalination plant in the delta with the hope of procuring 30% of its water there. Kurtis Alexander, San Francisco Chronicle, 18 Sep. 2022 Two communities with a combined population of about 700 were threatened but no mandatory evacuations were ordered in what became the largest wildfire ever in the delta at 259 square miles (671 square kilometers). Mark Thiessen, Anchorage Daily News, 25 July 2022 Two communities with a combined population of about 700 were threatened but no mandatory evacuations were ordered in what became the largest wildfire ever in the delta at 259 square miles. Mark Thiessen, BostonGlobe.com, 25 July 2022 Previous strains like alpha, beta and delta fell under the convention. Bloomberg News, oregonlive, 7 Jan. 2023 See More

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.

Word History

Etymology

Noun and Adjective (1)

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

First Known Use

Noun

12th 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

Time Traveler
The first known use of delta was in the 12th century

Dictionary Entries Near delta

Cite this Entry

“Delta.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/delta. Accessed 25 Mar. 2023.

Kids Definition

delta

noun
del·​ta
ˈdel-tə
1
: the 4th letter of the Greek alphabet
Δ or ƍ
2
: something shaped like a capital Δ
especially : the triangular or fan-shaped piece of land made by deposits of mud and sand at the mouth of a river
deltaic
del-ˈtā-ik
adjective

Medical Definition

delta

1 of 2 noun
del·​ta ˈdel-tə How to pronounce delta (audio)
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
3
4
also Delta : delta variant

delta

2 of 2 adjective
variants or ƍ-
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

Geographical Definition

Delta

geographical name

Del·​ta ˈdel-tə How to pronounce Delta (audio)
1
municipality south and southeast of Vancouver in southwestern British Columbia, Canada population 99,863
2

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