The term height refers to the vertical position of the tongue body when the vowel or consonant is pronounced. Usually three heights are distinguished: high, low, and mid. [i, ɪ, ʊ, u] are the high vowels of English. [e, ɛ, ɔ, o, ʌ, ə] are the mid vowels of English, and [æ, ɑ] are the low vowels of American English (other dialects have other low vowels).
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- Matthews, P. H. (1997) The Concise Oxford Dictionary of Linguistics. Oxford: Oxford University Press.
- Ladefoged, D. (2010) A Course in Phonetics. 6th Edition. Wadsworth Publishing.