Upsilon – Υ υ
Upsilon is a flexible letter with evolving applications. The classic pronunciation to ancient Greeks is like the sound of a long “U” in the Latin alphabet. Think of the “U” sound in words like “ruse” or “dune.” However, modern pronunciations are closer to a long “E” sound.
Upsilon is the twentieth letter of the Greek alphabet. Its numerical value is 400. The letter is used to represent mass to light. Upsilon also lends its script to the Airies symbol.