The description of vowel sounds in phonetics involves several key dimensions. The height of the tongue during sound production categorizes these sounds as high, mid, or low. Another important dimension is the frontness or backness, which indicates whether the tongue is positioned towards the front, central, or back part of the mouth.
Height refers to the relative height of the relevant part of the tongue when producing a sound: high, mid, low. Frontness and backness refers to the part of the mouth part of the
tongue move toward: front, central, and back. Tenseness refers to whether the lip/tongue muscles are relatively tensed or relaxed when producing a vowel sound: tense and lax.