Υ

Upsilon (uppercase Υ, lowercase υ; Greek: , ýpsilon, [ˈipsilon]; /ˈʌpsᵻlɒn, ˈjuːp-, ˈuːp-, ˈʊp-, -lən/; or UK /ʌpˈsaɪlən, juːp-/) is the 20th letter of the Greek alphabet. In the system of Greek numerals, Υʹ has a value of 400. It is derived from the Phoenician waw .