The front–back dimension

Front vowels are produced with the front of the tongue raised towards the hard palate (although not raised enough, remember, to obstruct the airflow and cause local friction; vowels are approximants). The vowels in (1) are front. These could, in principle, equally be described as palatal, and this might be helpful in making phonological rules transparent, the rule palatalising velar /k g/ before front vowels in kitchen, key, give, geese looked rather perplexing as the relationship between palatal and front was not obvious. However, calling front vowels palatal would be misleading, since frontness covers a larger area than [palatal], as we shall see below; and it contrasts with completely different alternatives, namely central and back, rather than labial, alveolar, dental, velar and so on.

Conversely, back vowels have the back of the tongue raised, towards the soft palate or velum. The vowels in (2) are back.

There is also a class of vowels between front and back: these are known as central vowels, and involve a raising of the body of the tongue towards the area where the hard and soft palate join. Central vowels are exemplified in (3). The most common of these in English, [ə], is known as schwa, and only appears in unstressed syllables.