Vowels beside dots are: unrounded  rounded

The open front unrounded vowel, or low front unrounded vowel,[1] is a type of vowel sound, used in some spoken languages. It is one of the eight primary cardinal vowels, not directly intended to correspond to a vowel sound of a specific language but rather to serve as a fundamental reference point in a phonetic measuring system.[2]

The symbol in the International Phonetic Alphabet (IPA) that represents this sound is ⟨a⟩, and in the IPA vowel chart it is positioned at the lower-left corner. However, the accuracy of the quadrilateral vowel chart is disputed, and the sound has been analyzed acoustically as extra-open at a position where the front/back distinction has lost its significance. There are also differing interpretations of the exact quality of the vowel: the classic sound recording of [a] by Daniel Jones is slightly more front but not quite as open as that by John Wells.[3]

In practice, it is considered normal by many phoneticians[who?] to use the symbol ⟨a⟩ for an open central unrounded vowel and instead approximate the open front unrounded vowel with ⟨æ⟩ (which officially signifies a near-open front unrounded vowel).[4] This is the usual practice, for example, in the historical study of the English language. The loss of separate symbols for open and near-open front vowels is usually considered unproblematic, because the perceptual difference between the two is quite small, and very few languages contrast the two. If there is a need to specify the backness of the vowel as fully front one can use the symbol ⟨æ̞⟩, which denotes a lowered near-open front unrounded vowel.

The Hamont-Achel dialect of Limburgish has been reported to contrast long open front, central and back unrounded vowels.[5] This is extremely unusual.