Delta (letter)

From Freepedia

Greek alphabet
Α α Alpha	Β β Beta
Γ γ Gamma	Δ δ Delta
Ε ε Epsilon	Ζ ζ Zeta
Η η Eta	Θ θ Theta
Ι ι Iota	Κ κ Kappa
Λ λ Lambda	Μ μ Mu
Ν ν Nu	Ξ ξ Xi
Ο ο Omicron	Π π Pi
Ρ ρ Rho	Σ σ Sigma
Τ τ Tau	Υ υ Upsilon
Φ φ Phi	Χ χ Chi
Ψ ψ Psi	Ω ω Omega
obsolete letters
Ϝ ϝ Digamma	Ϻ ϻ San
Ϙ ϙ Qoppa	Ϡ ϡ Sampi

Delta (upper case Δ, lower case δ) is the fourth letter of the Greek alphabet. In the system of Greek numerals it has a value of 4.

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 change or difference between mathematical values:

<math>m = {x_2-x_1 \over y_2-y_1} = {\Delta x \over \Delta y} </math>

• 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.
• Deflection in engineering mechanics
• A mark for deletion in proofreading. The usage is said to date back to classical times.

Letters that arose from Delta include the Roman D and the Cyrillic letter Д.