The term neutral vowel usually refers to an unstress
ed vowel sound
, represented in pronunciation guide
s like the International Phonetic Alphabet
by the schwa symbol
/ə/. In phonetics
, the schwa is defined as a mid-central unrounded monophthong
, a vowel phoneme
formed with the tongue
in the rest position, with lips unrounded; for example, the io
n or the a
More generally, a neutral vowel may refer to any unstressed vowel sound with an indefinite quality, such as the close central unrounded vowel /ɨ/ (roses, orange in certain accents).1 As far as I'm aware, "neutral vowel" when used in this sense is not a formally defined term.
In the study of vowel harmony, a neutral vowel is a vowel that may occur with front and back vowels in a given word.
1"neutral, n. and adj.". OED Online. November 2010. Oxford University Press. 9 December 2010