Uk (Cyrillic)
Uk (Ѹ ѹ; italics: Ѹ ѹ) is a letter of the early Cyrillic alphabet. It was originally a digraph of the Cyrillic letters O (О о) and U (У у) or less frequently O and Izhitsa (Ѵ ѵ). To save space, it was often written as a vertical ligature (Ꙋ ꙋ), called "monograph Uk". In modern times, ⟨оу⟩ has been replaced by the simple ⟨у⟩.
In later manuscripts, the digraph Uk has three cases: lowercase ⟨ѹ⟩, uppercase ⟨Ѹ⟩, and an all-caps form which is used in all-capitals titles ⟨ОУ⟩.
Read more about Uk (Cyrillic): Borrowing From Greek, Development of The Use of Uk in Old East Slavic, Representation On Computers, Computing Codes