Editing Vowel (section)

=== Backness ===
[[File:Cardinal vowel tongue position-front.svg|thumb|upright=0.9|Idealistic tongue positions of [[Cardinal vowel|cardinal]] front vowels with highest point indicated]]
Vowel backness is named for the position of the tongue during the articulation of a vowel relative to the back of the mouth. As with vowel height, however, it is ''defined'' by a formant of the voice, in this case the second, F2, not by the position of the tongue. In front vowels, such as {{IPA|[i]}}, the frequency of F2 is relatively high, which generally corresponds to a position of the tongue forward in the mouth, whereas in back vowels, such as {{IPA|[u]}}, F2 is low, consistent with the tongue being positioned towards the back of the mouth.

The [[International Phonetic Alphabet]] defines five degrees of vowel backness (sorted according to backness, with the top-most one being the front-most back and the bottom-most being the back-most):
* [[front vowel|front]]
* [[near-front vowel|near-front]]
* [[central vowel|central]]
* [[near-back vowel|near-back]]
* [[back vowel|back]]

To them may be added front-central and back-central, corresponding to the vertical lines separating central from front and back vowel spaces in several IPA diagrams. However, ''front-central'' and ''back-central'' may also be used as terms synonymous with ''near-front'' and ''near-back''. No language is known to contrast more than three degrees of backness nor is there a language that contrasts front with near-front vowels nor back with near-back ones.

Although some English dialects have vowels at five degrees of backness, there is no known language that distinguishes five degrees of backness without additional differences in height or rounding.