Tongue placement explained:

• High, high-mid, low-mid, and low refer to the vertical height of the tongue. For example, in a "high" vowel, the tongue would be closer to the palates and in a "low" vowel the tongue would be closer to the floor of the mouth

• Front, central, and back refer to the horizontal direction of the tonuge. For example, in a "front" vowel the tongue would be closer to the lips or the teeth and in a "back" vowel, the tongue would be retracted toward the velum

Diphthong: "moving vowel" that is pronounced as one vowel that transitions into another