Retroflex consonant

Finally, both sibilant (fricative or affricate) and nonsibilant (stop, nasal, lateral, rhotic) consonants can have a retroflex articulation.

The greatest variety of combinations occurs with sibilants, because for them, small changes in tongue shape and position cause significant changes in the resulting sound.

The farther back the point of contact with the roof of the mouth, the more concave is the shape of the tongue, and the duller (lower pitched) is the sound, with subapical consonants being the most extreme.

The last type has a groove running down the center line of the tongue, which gives it a strong hissing quality.

The retroflex sounds, however, have a flat or concave shape, with no associated palatalization, and no groove running down the tongue.

Retroflex consonants are transcribed in the International Phonetic Alphabet as follows: Some linguists restrict these symbols for consonants with subapical palatal articulation, in which the tongue is curled back and contacts the hard palate, and use the alveolar symbols with the obsolete IPA underdot symbol for an apical post-alveolar articulation: ⟨ṭ, ḍ, ṇ, ṣ, ẓ, ḷ, ɾ̣, ɹ̣⟩, and use ⟨ᶘ, ᶚ⟩ for laminal retroflex, as in Polish and Russian.

Consonants with more forward articulation, in which the tongue touches the alveolar or postalveolar region rather than the hard palate, can be indicated with the retracted diacritic (minus sign below).

This occurs especially for [s̠ ẕ]; other sounds indicated this way, such as ⟨ṉ ḻ ḏ⟩, tend to refer to alveolo-palatal rather than retroflex consonants.

Retroflex consonants are largely absent from indigenous languages of the Americas with the exception of the extreme south of South America, an area in the Southwestern United States as in Hopi and O'odham, and in Alaska and the Yukon Territory as in the Athabaskan languages Gwich’in and Hän.

In southwest Ethiopia, phonemically distinctive retroflex consonants are found in Bench and Sheko, two contiguous, but not closely related, Omotic languages.

An exception, however, is the Toda language, with a two-way distinction among retroflex sibilants between apical (post)alveolar and subapical palatal.