A retroflex consonant is a coronal consonant where the tongue has a flat, concave, or even curled shape, and is articulated between the alveolar ridge and the hard palate. They are sometimes referred to as cerebral consonants, especially in Indology. Other terms occasionally encountered are domal and cacuminal.In the International Phonetic Alphabet, retroflex consonants are indicated with a hook in the bottom right, such as [ʂ ʐ ʈ ɖ ɳ ɭ ɽ ɻ]. Alternatively, especially for those sounds with a relatively forward articulation (e.g. in the alveolar or postalveolar region rather than the hard palate), they can be indicated with a retracted diacritic (underbar); this occurs especially for [s̱ ẕ]. (Other sounds indicated this way, such as [ṉ ḻ ḏ], tend to refer to alveolo-palatal rather than retroflex consonants.)