The Dravidian languages retain most of the contrasts of Proto-Dravidian vowels and consonants. Proto-Dravidian had five vowels/i e a o u/ with length contrast /ˉ/. Alternatively, one can set up ten vowels for Proto-Dravidian, five short and five long. Diphthongs [ai au] can be treated as sequences of a vowel + a semiconsonant, i.e. /ay aw/ patterning with VC. There were seventeen consonants in Proto-Dravidian: six stops /p t ṯ ṭ c k/, four nasals /m n ṇ ñ/, two laterals /l ḷ/, one flap /r/, one retroflex frictionless continuant /ẓ/, three semivowels /w y H/. The last one is a laryngeal, which patterns phonologically with semivowels. All departures from this system can be traced to two sources: (a) certain sound changes within the historical period of individual languages or subgroups; (b) borrowing from contact languages, either of the same family or of a different family.
The five-vowel system is fairly stable in all subgroups; new centralized vowels have been added, through splits, to the list of phonemes of several of the Nilgiri languages, namely Toda, Iruḷa, Kuṟumba of South Dravidian I. Long vowels are less subject to change than the short vowels. Four of the stops have remained stable in the whole family: /p t ṭ k/. The affricate /c/ gets variable treatment in different subgroups, represented as [ts c s]. The alveolar /ṯ/ also has undergone change and has been eliminated as a distinctive unit outside South Dravidian.
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