What kinds of vowels occur in the Nakho-Dagestanian languages?

The vowel systems of the Nakho-Dagestanian languages are characterized by significant diversity. While some languages utilize up to five cardinal vowels (a, e, i, o, u), with o sometimes functioning as a developing independent unit, others exhibit more complex structures.1

Specific variations include:
* Long and nasalized vowels: Found in the Andi languages.1
* Pharyngealized vowels: Present in Udi.1
* Labialized vowels: Characteristic of the Dido languages.1
* Intricate systems: The Nakh languages, such as Chechen, feature highly complex systems that can include up to 30 distinctive vowels, encompassing diphthongs and triphthongs.1

Generally, there is an inverse relationship between the complexity of a language's vowel system and its consonant system; languages with highly developed vowel systems, such as Chechen, Ingush, and Dido, tend to have comparatively simpler consonant systems, whereas those with complicated consonantisms often possess simpler vowel systems.1