O (Mongolic)
O is a letter of related and vertically oriented alphabets used to write Mongolic and Tungusic languages. Mongolian language 

 Transcribes Chakhar ; Khalkha , , and . Transliterated into Cyrillic with the letter . Indistinguishable from , except when inferred by its placement: it is only found in medial or final syllables if the initial syllable also carries it, or rarely when it carries the vowel . = the final form used in loanwords, as in   ( ). = medial form used after the junction in a proper name compound. Derived from Old Uyghur waw (), preceded by an aleph () for isolate and initial forms. Produced with  using the Windows Mongolian keyboard layout. In the Mongolian Unicode block,  comes after  and before . Clear Script

Xibe language

Manchu language

Notes

References 

Articles containing Mongolian script text
Mongolic letters
Mongolic languages
Tungusic languages