Upsilon: Twentieth 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.

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. 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.

• U (Cyrillic)