Xi

Xi (uppercase/lowercase Ξ ξ) is the 14th letter of the Greek alphabet. It is used to represent the "x" sound in Ancient and Modern Greek. In the system of Greek numerals, it has a value of 60. The Roman letter X and Cyrillic letter Ѯ came from Xi.

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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
Other letters
Ϝϝ Digamma Ⱶⱶ Heta
Ϻϻ San Ϙϙ Koppa
Ϡϡ Sampi Ϛϛ Stigma
Ϸϸ Sho

In mathematics, both uppercase Ξ and lowercase ξ are used to refer to variants of Riemann Xi function (itself a variant of Riemann zeta function).[1] In physics, the uppercase Ξ is used to represent the cascade particle and xi baryon.[2]

References

  1. "Greek/Hebrew/Latin-based Symbols in Mathematics". Math Vault. 2020-03-20. Retrieved 2020-10-06.
  2. "Xi Symbol in Greek Alphabet". www.greeksymbols.net. Retrieved 2020-10-06.