delta
1 of 4noun
del·ta ˈdel-tə 
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)
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
Suresh V. Kuchipudi deltaic
del-ˈtā-ik
adjective delta
2 of 4adjective (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 4communications code word
—used as a code word for the letter d
Delta
4 of 4adjective (2)
: of, relating to, or characteristic of the The Delta region of Mississippi
Example Sentences
Recent Examples on the Web Sammy Rothstaff Writer, Los Angeles Times, 15 Sep. 2022 Up next for Aperta is the delta prototype, which will basically be the production version of the vehicle, according to Electrek. Bryan Hood, Robb Report, 12 Sep. 2022 Farther downlake, the San Juan River, a major tributary that joins the reservoir, has pushed its delta closer to Lake Powell’s main channel. AZCentral.com, 6 Sep. 2022 In fall 2021, the dangerous delta variant dominated, to be replaced later that year by omicron, which caused the highest caseload and number of deaths of the pandemic. Karen Weintraub, USA TODAY, 1 Sep. 2022 Niger delta cuisine is evident in the old traditional palm fruit dishes such as owo and banga soups and banga rice. Uwagbale Edward-ekpu, Quartz, 2 Sep. 2022 Both 2019 and 2021′s Labor Day weekends saw comparatively low hotel occupancy, due to Hurricane Dorian in 2019 and the delta COVID-19 variant last year, Matej said. Katie Rice, Orlando Sentinel, 1 Sep. 2022 Additionally, the weekend is down more than 16 percent from the same frame in 2021, when the COVID-19 delta variant was much more of an issue in terms of moviegoing. Pamela Mcclintock, The Hollywood Reporter, 27 Aug. 2022 The team’s signature aerial maneuvers include diamond and delta formations. Kori Rumore, Chicago Tribune, 18 Aug. 2022 See More
Noun
Yolo Bypass is supposed to help an endangered fish, the delta smelt — but critics see it as a canard meant to benefit Westlands Water District, an agricultural powerhouse. Sammy Rothstaff Writer, Los Angeles Times, 15 Sep. 2022 Up next for Aperta is the delta prototype, which will basically be the production version of the vehicle, according to Electrek. Bryan Hood, Robb Report, 12 Sep. 2022 Farther downlake, the San Juan River, a major tributary that joins the reservoir, has pushed its delta closer to Lake Powell’s main channel. AZCentral.com, 6 Sep. 2022 In fall 2021, the dangerous delta variant dominated, to be replaced later that year by omicron, which caused the highest caseload and number of deaths of the pandemic. Karen Weintraub, USA TODAY, 1 Sep. 2022 Niger delta cuisine is evident in the old traditional palm fruit dishes such as owo and banga soups and banga rice. Uwagbale Edward-ekpu, Quartz, 2 Sep. 2022 Both 2019 and 2021′s Labor Day weekends saw comparatively low hotel occupancy, due to Hurricane Dorian in 2019 and the delta COVID-19 variant last year, Matej said. Katie Rice, Orlando Sentinel, 1 Sep. 2022 Additionally, the weekend is down more than 16 percent from the same frame in 2021, when the COVID-19 delta variant was much more of an issue in terms of moviegoing. Pamela Mcclintock, The Hollywood Reporter, 27 Aug. 2022 The team’s signature aerial maneuvers include diamond and delta formations. Kori Rumore, Chicago Tribune, 18 Aug. 2022 See More 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
Phrases Containing delta
Kids Definition
delta
noun
del·ta ˈdel-tə
: 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
Medical Definition
delta 1 of 2
noun
del·ta ˈdel-tə
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
: delta wave
4
also Delta : delta variant
delta
2 of 2adjective
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
1
municipality south and southeast of Vancouver in southwestern British Columbia, Canada population 99,863
2
see delta, the