Ou (ligature)

Ou (Majuscule: Ȣ, Minuscule: ȣ) is a ligature of the Greek letters omicron ⟨ο⟩ and upsilon ⟨υ⟩ which was frequently used in Byzantine manuscripts to indicate a close back rounded vowel [u]. The ο–υ ligature is still seen today on icon artwork in Greek Orthodox churches, and sometimes in graffiti or other forms of informal or decorative writing.

In printed works, the ligature is often replaced by Ʊ, an inverted omega.