delta

1 of 4

noun

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)

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

del-ˈtā-ik 

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

Examples of delta in a Sentence

Recent Examples on the Web

Noun

Yet, while its baobab trees, lions and gorillas, and deltas like the Okavango have long captured the world’s imaginations, its cities have been too often overlooked by travelers from beyond the continent, despite being equally exciting cultural ecosystems, and destinations in their own right. —Arati Menon, Condé Nast Traveler, 9 Dec. 2024

But this is the desert, where a little water can summon life, and for years, conservation groups on both sides of the international boundary have worked to create new flows into the delta. —Shaun McKinnon, The Arizona Republic, 28 Oct. 2024

Louisiana Congressional District 1 Louisiana’s 1st district covers land from the northern shore of Lake Pontchartrain south to the Mississippi River delta. —Andrew Depietro, Forbes, 1 Oct. 2024

Bangladesh is a low-lying delta nation crisscrossed by about 230 rivers, including more than 50 that cross borders. —Binaj Gurubacharya, Los Angeles Times, 30 Sep. 2024

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

• delta agent
• delta hepatitis
• delta ray
• delta variant
• delta virus
• delta wave
• delta wing
• hepatitis delta virus
• Kronecker delta

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 

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 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 

1

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

2

see delta, the