Open central unrounded vowel
The open central unrounded vowel, or low central unrounded vowel, is a type of vowel sound, used in many spoken languages. While the International Phonetic Alphabet officially has no dedicated letter for this sound between front and back , it is normally written . If precision is required, it can be specified by using diacritics, typically centralized . However, it has been argued that the purported distinction between a front and central open vowel is based on outdated phonetic theories, and that cardinal is the only open vowel, while , like , is a near-open vowel. It is usual to  use plain for an open central vowel and, if needed, for an open front vowel. Sinologists may use the letter (small capital A). The IPA has voted against officially adopting this symbol in 1976, 1989, and 2012. The Hamont-Achel dialect of Limburgish has been reported to contrast long open front, central and back unrounded vowels. This is extremely unusual. Features. This often subsumes open (low) front vowels, because the tongue does not have as much flexibility in positioning as it does for the close (high) vowels; the difference between an open front vowel and an open back vowel is  equal to the difference between a close front and a close central vowel, or a close central and a close back vowel. Occurrence. Most languages have some form of an unrounded open vowel. Because the IPA uses for both front and central unrounded open vowels, it is not always clear whether a particular language uses the former or the latter. However, there may not actually be a difference. (See Vowel#Acoustics.)