5 Vowels: Backness/Advancement

Tongue advancement (sometimes called “backness”) refers to how far back the raised portion of the tongue is when producing a vowel. The /i/ vowel (as in “heat”) is very far forward and is described as a “front” vowel. The /u/, on the other hand is a “back vowel” and the tongue is raised up at the back of the oral cavity as in the word “boot.”