Back vowel

In strict IPA usage, the open front unrounded vowel is and the open back unrounded vowel is . However, many phonological traditions use (or the letter ⟨a⟩) more loosely for a low vowel, and recommend clarifying front vs. central/back values when the distinction is important. In descriptions of backness-based vowel harmony, a low vowel written /a/ may pattern with the back-vowel set even when its phonetic realization is not narrowly transcribed as . ==Phonology==

Vowel backness is often treated as a distinctive feature (commonly [±back]) and can participate in processes such as vowel harmony, where vowels within a domain (often the word) systematically agree for backness and sometimes other properties. Back vowels form a class defined by tongue-body retraction, but they may differ in vowel height (e.g. close vs. open ) and rounding; intermediate degrees of retraction and centralization can be transcribed with IPA diacritics for relative advancement or retraction and centralization (e.g. , , ), and some phonetic descriptions further distinguish types of rounding (e.g. protrusion vs. labial compression). ==Acoustics and perception==

The vowel diagram used in IPA description is primarily a reference space for perceived vowel quality and does not directly encode vocal-tract shapes. Acoustically, perceived vowel backness is correlated (roughly) with the second formant (F2), with back vowels tending to have lower F2 values than front vowels. Lip rounding lowers vocal-tract resonances and can reinforce the acoustic profile associated with back vowels, which has been argued to support the common co-occurrence of backness and rounding. ==Partial list==

Back (and near-back) vowels with dedicated IPA symbols include: • close back unrounded vowel • close back rounded vowel • near-close near-back rounded vowel • close-mid back unrounded vowel • close-mid back rounded vowel • open-mid back unrounded vowel • open-mid back rounded vowel • open back unrounded vowel • open back rounded vowel Vowels without dedicated IPA letters can be transcribed using diacritics for relative articulation (e.g. , , ). ==See also==