del·​ta | \ˈdel-tə \

Definition of delta 

(Entry 1 of 4)

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 4)


: fourth in position in the structure of an organic (see organic entry 1 sense 3b(1)) molecule from a particular group or atom symbol ƍ


communications code word

Definition of Delta (Entry 3 of 4)

used as a code word for the letter d


geographical name
Del·​ta | \ˈdel-tə \

Definition of Delta (Entry 4 of 4)

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 \ adjective

Examples of delta in a Sentence

Recent Examples on the Web: Noun

The National Marine Fisheries Service works with the state to protect the delta smelt and Chinook salmon, two fish species under threat because of California's drought, according to ABC News. Jonathan Hunt, Fox News, "Commerce chief scolds California over environmental policies he says hinder firefighters: ‘Lives are at stake’," 9 Aug. 2018 The actual amount of delta that’s grown there over the course of decades is only about 6 square miles. Nate Berg, Curbed, "Can engineering save Louisiana’s coastline?," 7 Nov. 2018 The new estimate would mean that anywhere between 3.8 million and more than 10 million gallons of oil a year are leaking into the water at the site, known as Mississippi Canyon-20, south of the Mississippi River delta. Ted Mann, WSJ, "Oil Spill at Center of Legal Battle Worse Than Earlier Estimated, Study Finds," 14 Sep. 2018 To do the same mission through the Gateway, both coming and going, requires a delta-v of 10.65km/s, a 17 percent increase. Eric Berger, Ars Technica, "NASA says it’s building a gateway to the Moon—critics say it’s just a gate," 6 Sep. 2018 Water diversion also contributes to increased salinity of delta ecosystems. Kristine Phillips, The Seattle Times, "Wildfires continue to char California, but one fire is in a destructive league of its own," 7 Aug. 2018 Or as if the Appalachian Mountains were actually a massive river, and this crescent was its delta. Dino Grandoni, Washington Post, "The Energy 202: Scott Pruitt is still under investigation by EPA watchdog," 13 July 2018 In San Francisco Bay, halibut are roaring in from the ocean and striped bass from the delta, both on a mission to feast on new arrivals of anchovies and provide a great start to the summer fishing season. Tom Stienstra, San Francisco Chronicle, "Summer arrives: Light the fuse and stand back," 31 May 2018 The Amazon runs over 4,300 miles from its headwaters in the Andes to its massive delta on the Atlantic. Ken Jennings, Condé Nast Traveler, "Why the Amazon River Can't Be Crossed By Bridge," 9 Apr. 2018

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


circa 1929, in the meaning defined above

Communications code word

1952, in the meaning defined above

History and Etymology for delta


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


see delta entry 1

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Statistics for delta

Last Updated

7 Dec 2018

Look-up Popularity

Time Traveler for delta

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

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More Definitions for delta



Financial Definition of delta

What It Is

Delta is the ratio comparing the change in price of an underlying asset to the change in price of a derivative. It is one of the four main statistics, known as "Greeks," used to analyze derivatives.

How It Works

Let's assume you own a call option on Company XYZ stock. If the price of Company XYZ stock increased by $1.00 and the call option increased by $0.80 in the same time period, then the delta is 0.80 ($0.80/$1.00).

The definition of delta on InvestingAnswersPut options work inversely. Since put options lose value as the underlying security increases, delta is a negative number. If a stock increases $1.00, and the put price decreases $0.50, then the put option has a delta of -0.50. Deltas aren't constant and change according to fluctuations in the underlying stock's price, time left on the derivative until expiration, and volatility in the underlying stock.

Why It Matters

Delta allows derivatives traders to understand what sort of risk/return they can expect from an investment. For instance, if they believe a stock will increase $2.00 per share in the near future, they can buy a call option on the stock. By using the delta calculation, the investor can calculate their potential gain from the stock's move -- important information to know before taking a risk.

Source: Investing Answers



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

: an area of low land along the Mississippi River that is mainly in the state of Mississippi


del·​ta | \ˈdel-tə \

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

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del·​ta | \ˈdel-tə \

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

Spanish Central: Translation of delta

Nglish: Translation of delta for Spanish Speakers

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

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