What is O-hook?

O-hook is a letter of the Cyrillic script. It is derived from the initial form of the Arabic letter hāʾ, ⟨ه‍⟩. In the Unicode text-encoding standard, this letter is called "Abkhazian Ha". Its form bears some similarities to the Greek letter Theta. In English, O-hook is commonly romanized using the Latin letter O with dot below but its ISO 9 transliteration is the Latin letter O with grave accent.

O-hook is used in the alphabet of the Abkhaz language where it represents the labial-palatal approximant /ɥ/, the sound of ⟨ui⟩ in French "huit" ]. It is placed between O and Π in the alphabet.