Noun
(phonetics) Quality of being a back vowel.
Antonym: frontness
Andrew Spencer (1996), Phonology: theory and description, p. 25 :
The most important aspects of vowel quality are tongue height, frontness/backness and lip rounding.
(phonetics) A quality of vowels, indicating the horizontal position of the tongue relative to the back of the mouth (front, near-front, central, near-back, or back).
Synonym: frontness
Coordinate terms: (vertical dimension) height, (lip articulation) roundedness, length, nasalization, reduction
Although English has vowels at five degrees of backness, there is no known language that distinguishes five degrees of backness without additional differences in height or rounding. Source: Internet
For instance, Altaic languages are proposed to have a rounding harmony superimposed over a backness harmony. Source: Internet
From vowel harmony it follows that the initial syllable of each single (non-compound) word controls the frontness or backness of the entire word. Source: Internet
In this type of vowel harmony, the position of the root of the tongue in regards to backness is the phonetic basis for the distinction between two harmonizing sets of vowels. Source: Internet
Nonetheless, even in those languages there is usually some phonetic correlation between rounding and backness: front rounded vowels tend to be more front-central than front, and back unrounded vowels tend to be more back-central than back. Source: Internet
Daniel Jones developed the cardinal vowel system to describe vowels in terms of the features of tongue height (vertical dimension), tongue backness (horizontal dimension) and roundedness (lip articulation). Source: Internet