Mid vowel

A mid vowel (or a true-mid vowel) is any in a class of vowel sounds used in some spoken languages. The defining characteristic of a mid vowel is that the tongue is positioned midway between an open vowel and a close vowel.

Other names for a mid vowel are lowered close-mid vowel and raised open-mid vowel, though the former phrase may also be used to describe a vowel that is as low as open-mid; likewise, the latter phrase may also be used to describe a vowel that is as high as close-mid.

Vowels
The only mid vowel with a dedicated symbol in the International Phonetic Alphabet is the mid central vowel with ambiguous rounding.

The IPA divides the vowel space into thirds, with the close-mid vowels such as or  and the open-mid vowels such as  or  equidistant in formant space between open  or  and close  or. Thus a true mid front unrounded vowel can be transcribed as either a lowered ⟨e̞⟩ (with a lowering diacritic) or as a raised ⟨ɛ̝⟩ (with a raising diacritic). Typical truly mid vowels are thus:


 * mid front unrounded vowel or
 * mid front rounded vowel or
 * mid central unrounded vowel or  (most commonly written ⟨ə⟩)
 * mid central protruded vowel or  (most commonly written ⟨ɵ⟩ as if it were close-mid)
 * mid central compressed vowel
 * mid back unrounded vowel or
 * mid back rounded vowel or

Languages
Few languages contrast all three heights of mid vowel, because it is rare for a language to distinguish more than four heights of true front or back vowels.

The Kensiu language spoken in Malaysia and Thailand is highly unusual in that it phonemically contrasts true-mid vowels with close-mid and open-mid vowels without differences in other parameters such as backness or roundedness.