The open back unrounded vowel, or low back unrounded vowel, is a type of vowel sound, used in some spoken languages. The symbol in the International Phonetic Alphabet that represents this sound is . The letter is called script a or handwritten a because it lacks the extra hook on top of a printed letter a, which corresponds to a different vowel, the open front unrounded vowel. Script a, which has a full length linear stroke on its right, should not be confused with turned script a, , which has the linear stroke on its left and corresponds to a rounded version of this vowel, the open back rounded vowel.
The open back unrounded vowel is the vocalic equivalent of the pharyngeal approximant .
In some languages (such as Azerbaijani, Estonian, Luxembourgish and Toda) there is the near-open back unrounded vowel (a sound between cardinal and ), which can be transcribed in IPA with or .