Upsilon: Greek Letter, Symbol, and Its Uses

Upsilon ('uppercase Υ, lowercase υ') is the 20th letter of the Greek alphabet. Its pronunciation in modern Greek is similar to the 'u' sound in 'put' or 'pull'. In ancient Greek, it was pronounced like the French 'u' or the German 'ü'.

In mathematics, upsilon is often used as a variable to represent a number or a function. It is also used to represent the potential energy in physics and the decay constant in nuclear physics.

In astronomy, the letter upsilon is used to designate stars in various constellations such as Upsilon Andromedae and Upsilon Sagittarii.

In computer science, upsilon is used as a symbol for the micro sign (µ) in some programming languages and text editors.