A palatalization-split consonant inventory is one where every or almost every non-palatal consonant has a phonemical palatalized counterpart. This setup occurs mostly in North-Central Asia, including Russian, Nenets and Khalkha Mongolian. (More limited palatalization contrasts are common in the area, too.)
Palatalization splits (and especially the more complex variants - see below), go frequently together with wholly or partly vertical vowel systems, with vowel frontness filled in from palatality of the preceding consonant, eg. /mʲi/ → [mʲi], but /mi/ → [mɨ]. It is these kind of languages where palatalized palatals are possible: this will be a segment that is both palatal in its articulation and imparts a palatal coloring: /ja/ → [ja], but /jʲa/ → [jɛ] vel. sim. Interaction with vowel harmony offers similar possibilities (perhaps implying a suprasegmental interpretation of palatality).
A palatalization split can come about by excessive diachronic palatalization followed by neutralization of the conditioning vowel contrasts (eg. /mi/ → /mʲi/, but /mɨ/ → /mi/). The neutralization does not need to be immediately phonetical, if apparent front/back vowel contrasts can now be explained in terms of vowel coloring by a consonant's palatalization. Thus, we have the following phases:
- Palatalization of many consonants
- Non-palatal consonants no longer occur before front vowels
- Palatalization is reanalyzed as a feature of the consonants rather than the vowels
- Vowel frontness is reanalyzed as resulting from consonant palatality
Not all languages can reach phase 4: this will be rendered impossible if palatalized consonants end up occurring also next to back vowels, via changes such as /Cju/ → /Cʲu/, or non-palatalized consonants end up occurring next to front vowels again, via changes such as /Cai/ → /Ce/.
Some corresponding pairs of consonants may differ in more than palatalization. For example, alveolars will commonly become postalveolar: /sʲ/ → [ʃ], or wholly palatal: /tʲ/ → [c]. (Irish has an example with velarity: /vˠ/ → [w].) Also near the apex of the palatal POA, some series may merge, leading to eg. non-palatal three-way distinction /p t k/ vs. palatal two-way distinction /pʲ c/.
More complex variations featuring other modes of secondary articulations are found dispersed over the world:
- Irish has no plain consonants, only palatalized and velarized variants.
- Marshallese takes this one step further with a palatalized/velarized/labialized tripartite division.
- Many Caucasian, especially Northwest Caucasian languages have idiosyncratic variations where certain but not all series can occur palatalized or labialized (typically, palatalized labial or coronal stops, or retroflex affricates, are lacking, as are labialized labials).