Noun
frontness (uncountable)
(phonetics) Quality of being a front vowel.
Andrew Spencer (1996), Phonology: theory and description, p. 25 :
The most important aspects of vowel quality are tongue height, frontness/backness and lip rounding.
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
However, in open vowels the high F1 frequency forces a rise in the F2 frequency as well, so an alternative measure of frontness is the difference between the first and second formants. Source: Internet