Delta_(letter)

Delta (letter)

Look up Δ, δ in Wiktionary, the free dictionary.

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
Obsolete letters
Digamma	Qoppa
San	Sampi

Greek diacritics

Delta (uppercase Δ, lowercase δ; Greek: Δέλτα [ðelta] Thelta) 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 arose from Delta include the Latin D and the equivalent in the Cyrillic alphabet: Д.

In Modern Greek it represents a voiced dental fricative /ð/, (like the th in the English word this) but in the Ancient Greek language, it represented a voiced dental plosive /d̪/.

A river delta is so named because its shape approximates the upper-case letter delta.

1 The upper-case letter Δ
2 The lower-case letter δ
3 See also
4 References

The upper-case letter Δ

The upper-case letter Δ can be used to denote:

Change; e.g. in:

${y_2-y_1\over x_2-x_1} = {\Delta y \over \Delta x}$ = the average change of y per unit x, i.e. the change of y over the change of x

More specifically, the difference operator.
The Laplace operator:

$\Delta f = \sum_{i=1}^n {\frac{\partial^2 f}{\partial x_i^2}}$

The discriminant of a polynomial equation, especially the quadratic equation:

$\Delta = b^2 - 4ac\,\!$

A macroscopic change in the value of a variable in mathematics or science
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
In legal shorthand, it represents a defendant
In the financial markets, it is one of the Greeks that describes the rate of change of an option price for a given change in the underlying benchmark
In genetics, it can stand for a gene deletion, e.g. the CCR5-Δ32 a deletion of the CCR5 at the 32nd bp segment
In chemistry, it denotes the change in a physical property such as heat, e.g ΔTemp would stand for the change in Temp
The American Dental Association cites it (together with omicron for "odont") as the symbol of dentistry. ^[1]

The lower-case letter δ

The lower-case letter δ can be used to denote:

An infinitesimal change in the value of a variable in mathematics or science
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
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
The Computer Science chapter at the Royal Institute of Technology^[2]

Contents

The upper-case letter Δ

The lower-case letter δ

See also

References