Delta (letter)

From Wikinfo

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
File:Digamma uc lc.svg	Digamma	File:Qoppa uc lc.svg	Qoppa
File:San uc lc.svg	San	File:Sampi uc lc.svg	Sampi
Other characters
File:Stigma uc lc.svg	Stigma	File:Sho uc lc.svg	Sho
File:Heta uc lc.svg	Heta
Greek diacritics

Delta (uppercase Δ lowercase δ), is the letter of the Greek alphabet, used to represent the "[d]" sound in Greek. In the system of Greek numerals it has a value of 4. Letters that came from it include the Roman D and Cyrillic Д.

A river delta is named after the letter delta because it has roughly the triangular shape of the upper-case delta.

The upper-case letter Δ is used as the symbol for:

• A macroscopic change in the value of a variable in mathematics or science.
• Any of the delta particles in particle physics.

The lower-case letter δ is used as the symbol for:

• A microscopic change in the value of a variable in mathematics or science.
• The Kronecker delta in mathematics.
• The Dirac delta function in mathematics.
• A mark for deletion in proofreading. The usage is said to date back to classical times.

References

• Adapted from the Wikipedia article, "Delta_(letter)" http://en.wikipedia.org/wiki/Delta_(letter), used under the GNU Free Documentation License