Delta (letter)

 ( Greek Letters ) 

Delta ( ; uppercase Δ, lowercase δ; , délta, ) is the fourth letter of the Greek alphabet. In the system of Greek numerals, it has a value of four. It was derived from the Phoenician letter dalet 𐤃. Letters that come from delta include the Latin alphabet D and the Cyrillic script Д.

A river delta (originally, the Nile Delta of the Nile River) is named so because its shape approximates the triangular uppercase letter delta. Contrary to a popular legend, this use of the word delta was not coined by Herodotus.

---

Pronunciation In Ancient Greek, delta represented a voiced dental plosive . In Modern Greek, it represents a voiced dental fricative , like the " th" in " that" or " this" (while in foreign words is instead commonly transcribed as ντ). Delta is romanized as d or dh.

---

Uppercase The uppercase letter Δ is used to denote:

• Change of any changeable quantity, in mathematics and the sciences (in particular, the difference operator online copy
  Michael Comenetz (2025). 9789810249045, World Scientific. ISBN 9789810249045
  ); for example, in $$

\frac{y_2-y_1}{x_2-x_1}=\frac{\Delta y}{\Delta x} , 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 and differentials, which also describe change by infinitesimal amounts.)

• The Laplace operator:
• : $\backslash Delta\; f=\backslash sum\_\{i=1\}^n\{\backslash frac\{\backslash partial^2f\}\{\backslash partial\; x\_i^2\}\}$.
• The discriminant of a polynomial equation, especially the quadratic equation:
  (2025). 9783540243267, Springer. . ISBN 9783540243267

(2025). 9780387403977, Springer-Verlag New York, Inc.. . ISBN 9780387403977

• : $\backslash Delta=b^2-4ac$.
• The area of a triangle:
• : $\backslash Delta=\backslash tfrac\{1\}\{2\}ab\backslash sin\{C\}$.
• The symmetric difference of two sets.
• A derivative 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.
• Any of the Delta baryon 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 forms.
• A simplex, simplicial complex, or convex hull.
• In chemistry, the addition of heat in a reaction.
• In legal shorthand, it represents a defendant.
  (2025). 9781285448947, Cengage Learning. . ISBN 9781285448947
• In the financial markets, one of the Greeks, describes the rate of change of an option price for a given change in the underlying benchmark.
• A major seventh chord in jazz music notation.
• In genetics, it can stand for a gene deletion (e.g. the CCR5-Δ32, a 32 nucleotide/bp deletion within CCR5).
• The American Dental Association cites it (together with omicron for "odont") as the symbol of dentistry.
• The anonymous signature of James David Forbes.Proceedings of the Royal Society, vol. XIX, p. ii.
• Determinacy (having a definite truth-value) in philosophical logic.
• In mathematics, the symbol ≜ (delta over equals) is occasionally used to define a new variable or function.

---

Lowercase The lowercase letter δ (or 𝛿) can be used to denote:

• A change in the value of a variable in calculus.
• A functional derivative in functional calculus.
• The (ε, δ)-definition of limits, in mathematics and more specifically in calculus.
• The Kronecker delta in mathematics.
• The central difference for a function.
• The degree of a vertex in graph theory.
• The Dirac delta function in mathematics.
• 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 F-ATPase.
• 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 ¹⁸O/¹⁶O and Deuterium/¹H from water are displayed using delta notation – δ¹⁸O and δD, respectively.
• The rate of depreciation of the aggregate capital stock of an economy in an exogenous growth model in macroeconomics.
• In a system that exhibits electrical reactance, the angle between voltage and Electric current.
• Partial charge in chemistry.
• The maximum birefringence of a crystal in optical mineralogy.
  NARDY, Antônio José Ranalli MACHADO, Fábio Braz (2025). 9788579752452, Oficina de Textos. ISBN 9788579752452
• An Old Irish voiced dental or alveolar fricative of uncertain articulation, the ancestor of the sound represented by Modern Irish dh.
• Silver ratio

---

Unicode

• ( in TeX)
• ( in TeX)

---

See also

• Arrow (symbol)
• Chevron (insignia)
• ∆ (disambiguation)
• D, d
• Д, д
• ẟ – Latin delta
• ∂ – the partial derivative symbol, a curved d, 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)
• Thorn (letter)
• Greek letters used in mathematics, science, and engineering
• ∇ – Nabla symbol
• Delta Air Lines
• SARS-CoV-2 Delta variant

Post Comment