Upsilon

Upsilon (uppercase/lowercase Υ υ) is the 20th letter of the Greek alphabet. It is used to represent the "u" sound in Ancient Greek and "i" in Modern Greek. In the system of Greek numerals, it has a value of 400. Letters that came from it include the Roman U, V and Y, and the Cyrillic У.

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
History
Archaic local variants Diacritics Ligatures Numerals ϛ (6) ϟ (90) ϡ (900)
Use in other languages
Bactrian Coptic Albanian
Related topics
Use as scientific symbols
Book Category Commons

In mathematics, the uppercase ${\displaystyle \Upsilon }$ is used to represent the upsilon function (a variant of Riemann zeta function), while the lowercase ${\displaystyle \upsilon }$ is used as a general variable.[1] In physics, the uppercase ${\displaystyle \Upsilon }$ is used to represent an upsilon meson. In astrology, the same letter is used for the sign of Aries.[2]