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. ATR vs RTR was once suggested to be the basis for the distinction between tense and lax vowels in European languages such as German, but Ladefoged and Maddieson have found that the tongue root position in Germanic languages is not an independent gesture.