The open-mid back rounded vowel is a type of vowel sound, used in some spoken languages. The symbol in the International Phonetic Alphabet that represents this sound is ɔ, and the equivalent X-SAMPA symbol is O. The IPA symbol is a turned letter c and both the symbol and the sound are commonly called "open-o". The name open-o represents the sound, in that it is like the sound represented by [o], the close-mid back rounded vowel, except it is more open. It also represents the symbol, which can be remembered as an o which has been "opened" by removing part of the closed circular shape.

Features of this vowel:

• Its vowel height is open-mid, which means the tongue is positioned halfway between an open vowel and a mid vowel.
• Its vowel backness is back, which means the tongue is positioned as far back as possible in the mouth in the mouth without creating a constriction that would be classified as a consonant.
• Its vowel roundedness is rounded, which means that the lips are rounded.

Occurs in:

• English (RP and GA) ball [bɔːl]
• French sort [sɔʀ] 'fate'
• German voll [fɔl] 'full'