Upsilon (US: , UK: ; uppercase Υ, lowercase υ; Greek: ύψιλον ýpsilon [ˈipsilon]) or ypsilon is the twentieth letter of the Greek alphabet. In the system of Greek numerals, Υʹ has a value of 400. It is derived from the Phoenician waw . Etymology. The name of the letter was originally just "υ" (y; also called hy, hence "hyoid", meaning "shaped like the letter υ"), but the name changed to "υ ψιλόν" u psilon 'plain υ' to distinguish it from οι, which had come to have the same [y] pronunciation. Pronunciation.
https://en.wikipedia.org/wiki/Upsilon
Upsilon (US: , UK: ; uppercase Υ, lowercase υ; Greek: ύψιλον ýpsilon [ˈipsilon]) or ypsilon is the twentieth letter of the Greek alphabet. In the system of Greek numerals, Υʹ has a value of 400. It is derived from the Phoenician waw . Etymology. The name of the letter was originally just "υ" (y; also called hy, hence "hyoid", meaning "shaped like the letter υ"), but the name changed to "υ ψιλόν" u psilon 'plain υ' to distinguish it from οι, which had come to have the same [y] pronunciation. Pronunciation.
