Advanced and retracted tongue root

In phonetics, advanced tongue root (ATR or +ATR), or expanded pharynx, and retracted tongue root (RTR or −ATR) are contrasting states of the pharynx during the pronunciation of vowels in some languages, especially in Western and Eastern Africa, but also in Kazakh and Mongolian.

[1] Advanced tongue root, abbreviated ATR or +ATR, also called expanded,[2] involves the expansion of the pharyngeal cavity by moving the base of the tongue forward, lowering the larynx, and otherwise expanding the walls of the pharynx during the pronunciation of a vowel.

As mentioned above, many African languages, such as Maasai, have systems of vowel harmony based on tongue root position.

In addition, the two vowels written e (/e̘/ and /i/) and o (/o̘/ and /u/) are often not distinguished and are approximately equivalent to European [e] and [o], as reflected in the orthography; for such people, the second harmonization rule does not apply.

[7] With advances in fiber-optic laryngoscopy at the end of the twentieth century, new types of phonation were discovered that involve more of the larynx than just the glottis.