Yu or Ju (Ю ю; italics: Ю ю or Ю ю; italics: Ю ю) is a letter of the Cyrillic script used in East Slavic and Bulgarian alphabets.
In English, Yu is commonly romanized as ⟨yu⟩ or ⟨ju⟩. In turn, ⟨ю⟩ is used, where available, in transcriptions of English letter ⟨u⟩ (in open syllables), and also of the ⟨ew⟩ digraph. The sound [y], like ⟨u⟩ in French and ⟨ü⟩ in German, may also be approximated by the letter ⟨ю⟩.
Omicron (US: /ˈoʊmɪkrɒn, ˈɒmɪkrɒn/ , UK: / oʊˈmaɪkrɒn/; uppercase Ο, lowercase ο, Greek: όμικρον) is the fifteenth letter of the Greek alphabet. This letter is derived from the Phoenician letter ayin: 
. In classical Greek, omicron represented the close-mid back rounded vowel [o] in contrast to omega, which represented the open-mid back rounded vowel [ɔː], and the digraph ⟨ου⟩ which represented the long close back rounded vowel [uː]. In modern Greek, both omicron and omega represent the mid back rounded vowel [o̞]. Letters that arose from omicron include Roman O and Cyrillic O and Ю. The name of the letter was originally οὖ (oû [ûː]), but it was later changed to ὂ μικρόν (ò mikrón 'small o') in the Middle Ages to distinguish the letter from omega ⟨ω⟩, whose name means 'big o', as both letters had come to be pronounced [o]. In modern Greek, its name has fused into όμικρον (ómikron). In the system of Greek numerals, it has a value of 70.