Backness is a binary feature associated with sounds pronounced with the body of the tongue pushed to the back of the mouth, usually with the tongue bunched up near the velum. Backness and its counterpart frontness are used to describe the articulatory movements required of vocalic segments. Although vowels are best described by their acoustic characteristics, binary features are enough to distinguish natural classes of vowels in a variety of languages.
English segments /u/ (as inboot), /ʊ/ (as in book), /o/ (as inboat), and /ɑ/ (as inpasta) are all back vowels. Backness can also be heard on consonants, notably sonorants like [l] whose dark L allophone ([ɫ]) is commonly produced following back vowels.
- Crystal, D. (2008) Dictionary of Linguistics and Phonetics. 6th Edition. Wiley-Blackwell.
- Ladefoged, D. (2010) A Course in Phonetics. 6th Edition. Wadsworth Publishing.