# Delta

letter in the Greek alphabet
(Redirected from Delta (letter))

Delta (uppercase/lowercase Δ δ), is a letter of the Greek alphabet, used to represent the "d" sound in Ancient and Modern 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.

 Greek alphabet Other letters Αα Alpha Νν Nu Ββ Beta Ξξ Xi Γγ Gamma Οο Omicron Δδ Delta Ππ Pi Εε Epsilon Ρρ Rho Ζζ Zeta Σσ 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 Ϝϝ Digamma Ϟϟ Koppa Ϛϛ Stigma Ϡϡ Sampi Ͱͱ Heta Ϸϸ Sho Ϻϻ San Category•Commons

In mathematics, the upper-case letter Δ can be used as symbol to represent "change" in a variable (e.g., ${\displaystyle \Delta x}$). It can also be used to represent discriminant—a key algebraic expression used to determine the number of roots a polynomial has. The lower-case letter ${\displaystyle \delta }$, on the other hand, is often used to denote small quantities in proofs involving limit, a key concept on calculus is based on.[1]

In molecular chemistry, the lower case Greek letter δ is used to represent a partial charge. This is always less than the unit charge associated with an ion, but has no real fixed value.

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

## References

1. "Compendium of Mathematical Symbols". Math Vault. 2020-03-01. Retrieved 2020-08-18.