Delta (letter)
{{#invoke:Hatnotehatnote}}Template:Main other {{ safesubst:#invoke:Unsubst$N=Refimprove date=__DATE__ $B= {{#invoke:Message boxambox}} }} Template:Sister
Greek alphabet  

Αα  Alpha  Νν  Nu 
Ββ  Beta  Ξξ  Xi 
Γγ  Gamma  Οο  Omicron 
Δδ  Delta  Ππ  Pi 
Εε  Epsilon  Ρρ  Rho 
Ζζ  Zeta  Σσς  Sigma 
Ηη  Eta  Ττ  Tau 
Θθ  Theta  Υυ  Upsilon 
Ιι  Iota  Φφ  Phi 
Κκ  Kappa  Χχ  Chi 
Λλ  Lambda  Ψψ  Psi 
Μμ  Mu  Ωω  Omega 
History  
Archaic local variants  
In other languages  
Scientific symbols  

Delta (uppercase Δ, lowercase δ or 𝛿; Δέλτα{{#invoke:Category handlermain}} Délta; Modern Greek Template:IPAel) is the fourth letter of the Greek alphabet. In the system of Greek numerals it has a value of 4. It was derived from the Phoenician letter dalet . Letters that come from delta include Latin D and Cyrillic Д.
A river delta (originally, the Nile River delta) is so named because its shape approximates the uppercase letter delta (the shape is a triangle). Despite a popular legend, this use of the word delta was not coined by Herodotus.^{[1]}
Pronunciation
In Ancient Greek, delta represented a voiced dental plosive /d/. In Modern Greek, it represents a voiced dental fricative /ð/, like the "th" in "that" or "this". It is romanized as d or dh.
Upper case
The uppercase letter Δ can be used to denote:
 Change of any changeable quantity, in mathematics and the sciences (more specifically, the difference operator{{ safesubst:#invoke:Unsubstdate=__DATE__ $B=
{{#invoke:Category handlermain}}{{#invoke:Category handlermain}}^{[citation needed]} }}); for example, in:
 the average change of y per unit x (i.e. the change of y over the change of x). Delta is the initial letter of the Greek word διαφορά diaphorá, "difference". (The small Latin letter d is used in much the same way for the notation of derivatives and differentials, which also describe change.)
 The Laplace operator:
 The discriminant of a polynomial equation, especially the quadratic equation:
 The symmetric difference of two sets
 A macroscopic change in the value of a variable in mathematics or science
 Uncertainty in a physical variable as seen in the uncertainty principle
 An interval of possible values for a given quantity (i.e. across a sample{{ safesubst:#invoke:Unsubstdate=__DATE__ $B=
{{#invoke:Category handlermain}}{{#invoke:Category handlermain}}^{[citation needed]} }})
 Any of the delta particles in particle physics
 The determinant of the matrix of coefficients of a set of linear equations (see Cramer's Rule)
 That an associated locant number represents the location of a covalent bond in an organic compound, the position of which is variant between isomeric forms
 A simplex, simplicial complex, or convex hull
 In chemistry, the addition of heat in a reaction
 In legal shorthand, it represents a defendant.
 In the financial markets, one of the Greeks, describing the rate of change of an option price for a given change in the underlying benchmark
 The symbol of the Greek inventor and architect Daedalus
 A major seventh chord in jazz music notation
 In genetics, it can stand for a gene deletion (e.g. the CCR5Δ32, a deletion of the CCR5 at the 32nd base pair segment)
 The American Dental Association cites it (together with omicron for "odont") as the symbol of dentistry.^{[2]}
 English indie rock band AltJ (so known because the symbol can be typed on a Mac OS X computer system by pressing AltJ)
Lower case
The lowercase letter δ (or 𝛿) can be used to denote:
 A change in the value of a variable in calculus
 An auxiliary function in calculus, used to rigorously define the limit or continuity of a given function
 The Kronecker delta in mathematics
 The Dirac delta function in mathematics
 In mathematics (specifically pointset topology), the boundary of a set A is denoted by δA .
 The transition function in automata
 Deflection in engineering mechanics
 The Force of interest in actuarial science
 The chemical shift of nuclear magnetic resonance in chemistry
 The relative electronegativity of different atoms in a molecule, δ^{−} being more electronegative than δ^{+}
 Text requiring deletion in proofreading; The usage is said to date back to classical times.
 In some of the manuscripts written by Dr. John Dee, the character of delta is used to represent Dee.
 A subunit of the F1 sector of the FATPase
 The declination of an object in the equatorial coordinate system of astronomy
 The dividend yield in the Black–Scholes option pricing formula
 Ratios of environmental isotopes, such as ^{18}O/^{16}O and D/^{1}H from water are displayed using delta notation – δ^{18}O and δD , respectively
 The rate of depreciation of the aggregate capital stock of an economy in an exogenous growth model in macroeconomics^{[3]}
 In a system that exhibits electrical reactance, the angle between voltage and current
Meteorology
 Delta was used as a name during the 1972 Atlantic hurricane season and the 2005 Atlantic hurricane season as Tropical Storm Delta (2005).
Keyboard Entry
On Microsoft Windows, a small delta can be generated by typing Template:Key pressTemplate:Key pressTemplate:Key press.
In certain programs (e.g. Microsoft Word), an uppercase delta can be typed using Template:Key pressTemplate:Key pressTemplate:Key pressTemplate:Key press. However, in most other programs, Template:Key pressTemplate:Key pressTemplate:Key pressTemplate:Key press generates a closing quotation mark (”).
Computer encodings
 Greek Delta / Coptic Dalda
 Latin Delta
 Technical and Mathematical symbols
 Mathematical Delta
These characters are used only as mathematical symbols. Stylized Greek text should be encoded using the normal Greek letters, with markup and formatting to indicate text style.
See also
 D, d
 Д, д
 ẟ  Latin delta
 ∂  the partial derivative symbol, sometimes mistaken for a lowercase Greek letter Delta.
 ð  the small eth appears similar to a small delta, and also represents a d sound in some contexts
 Th (digraph)
 Greek letters used in mathematics, science, and engineering
 ∇  Nabla symbol
References
 ↑ {{#invoke:Citation/CS1citation CitationClass=journal }}
 ↑ Caduceus, the emblem of dentistry  American Dental Association  ADA.org
 ↑ http://econ.duke.edu/people?subpage=unit&Gurl=%2Faas%2FEconomics&cname=Masters+Students