Postalveolar

From KneeQuickie

Postalveolar consonants are those articulated slightly further back than alveolar consonants, with the tip of the tongue against the roof of the mouth just behind the alveolar ridge.

Other than the postalveolar fricatives and the corresponding affricates, postalveolars rarely occur phonemically, as they are very similar in sound to alveolars. Indeed, even with the fricatives, in English the main difference between alveolar /s/ and postalveolar /ʃ/ is that the latter is labialized.

The IPA only has separate symbols for the postalveolar fricatives: /ʃ/ unvoiced and /ʒ/ voiced (X-Sampa /S/ and /Z/). Other postalveolar sounds can be written by adding the "retracted" diacritic (X-Sampa _-) to the symbol for the corresponding alveolar consonant.