In articulatory phonetics, sulcalization (from 'groove') is the pronunciation of a sound with a deep, longitudinal concavity (groove) down the back of the tongue (the dorsum), roughly opposite of the uvula. This is accomplished by raising the sides of the dorsum, and leaving a hollow along the midline.
This articulation has typically been associated with rhotics such as a 'bunched' or 'molar' and r-colored vowels, as well as 'dark' or 'throaty' quality sounds, either more velar-like (such as ) or more pharyngeal-like (such as ).
Occasionally, some linguists extend the term sulcalization to refer more broadly to the general presence of a longitudinal concavity of the tongue midline (see below). In this sense, sulcalization functionally contrasts with lateralization: sulcalization raises the sides of the tongue to direct airflow along the midline, whereas lateralization lowers the sides of the tongue to direct airflow over the sides. However, they are not necessarily mutually exclusive; for example, may involve both posterior dorsal sulcalization and anterior coronal lateralization.
No spoken language is known to make a phonemic distinction between sulcalized and ordinary vowels; though it has been reported that for some speakers of Received Pronunciation, the vowel , which is normally described as rounded, is pronounced with neutral or spread lips, and is instead given its characteristic quality through a "hollowing or sulcalization of the tongue-body." One scholar has also suggested that the vowel in the RP pronunciation of words like bird, typically transcribed , is actually a sulcal schwa, retaining the sulcality of the original rhotic consonant. Accordingly, the realization of the -element of the centring diphthongs , , in words such as near, pure and scare, is interpreted as the product of a loss of sulcality. Similarly, it has been noted that the rhotacized equivalent in American English is sulcalized.
Some linguists have referred to grooved fricatives, a similar but distinct articulatory concept, as sulcalized, though this should not be confused with the more common definition described in the section above. As with the more common definition of sulcalization, grooved fricatives also involve forming a groove down the center of the tongue (such as in some realizations of in the English words sit and case). They contrast with slit fricatives, which are pronounced with the tongue flat.
The groovedâÂÂslit distinction primarily applies to anterior consonants. Unlike the more common definition of sulcalization, which generally refers to a posterior hollowing, grooved fricatives involve raising the sides of the tongue to focus the turbulent airstream on the teeth, producing an anterior hollowing. This results in a more intense sound, typically associated with sibilants. Slit fricatives, with a flatter shape, have a wider and more dispersed airflow channel.
J. C. Catford observed that the degree of tongue grooving differs between places of articulation as well as between languages; however, no language is known to phonemically contrast fricatives based purely on the presence or absence of tongue grooving. Nonetheless, linguists sometimes make a phonetic distinction for certain fricative allophones that occur at the same place of articulation as a grooved or slit counterpart. For example, (a lenited allophone of found in some English dialects) is commonly described as slit, to distinguish it from grooved ; though it has also been noted that additional articulatory factors may go into the distinction between grooved and slit .
It was once proposed that the IPA include a diacritic to distinguish grooved and slit fricatives, but the proposal was rejected. While lacking diacritics for the feature specifically, the extIPA chart includes and to denote alveolar slit fricatives, which the authors have noted form a contrastive graphical pair with the more commonly seen and , denoting grooved dental fricatives.
Historically, the terms grooved fricative and sibilant have sometimes been treated as synonymous (and by extension, slit fricative and non-sibilant), though the reality of sibilant shapes is more complex; not all sibilants may share this feature, nor may it be unique to sibilants. For instance, is widely regarded to be characterized by a convex doming of the tongue rather than a concave grooving, and therefore has been defined as slit; conversely, ultrasound imaging has shown in English to exhibit grooving similar to , despite being typically regarded as slit.