The fifteen Katuic languages form a branch of the Austroasiatic languages spoken by about 1.3 million people in Southeast Asia. People who speak Katuic languages are called the Katuic peoples. Paul Sidwell is the leading specialist on the Katuic languages. He notes that Austroasiatic/Mon–Khmer languages are lexically more similar to Katuic and Bahnaric the closer they are geographically. He says this geographic similarity is independent of which branch of the family each language belongs to. He also says Katuic and Bahnaric do not have any shared innovations, so they do not form a branch of the Austroasiatic family.
In 1966, a lexicostatistical analysis of various Mon-Khmer languages in Indochina was performed by SIL linguists David Thomas and Richard Phillips. This study resulted in the recognition of two distinct new subbranches of Mon-Khmer, namely Katuic and Bahnaric (Sidwell 2009).
Data for adequate classification of the Mon–Khmer Katuic languages only become available after the opening of Laos to foreign researchers in the 1990s. The following classification is that of Sidwell (2005). Sidwell (2005) casts doubt on Diffloth's Vieto-Katuic hypothesis, saying that the evidence is ambiguous, and that it is not clear where Katuic belongs in the family. Additionally, Sidwell (2009) considers the Katu branch to be the most conservative subgroup of Katuic, while all the other branches have developed more innovations.
- Katu branch (Thap):
- Kui–Bru branch (West Katuic):
- Pacoh language (Tareng) (Vietnam and Laos)
- Ta'Oi–Kriang branch (Laos and Thừa Thiên-Huế, Vietnam):
Kuy and Bru each have around half a million speakers, while the Ta’Oi cluster has around 200,000 speakers.
Reconstructions of Proto-Katuic, or its sub-branches, include:
- Thomas (1967): A Phonology Reconstruction of Proto-East-Katuic
- Diffloth (1982): Registres, devoisement, timbres vocaliques: leur histoire en katouique
- Efinov (1983): Problemy fonologicheskoj rekonstrukcii proto-katuicheskogo jazyka
- Peiros (1996): Katuic Comparative Dictionary
- Therapahan L-Thongkum (2001): Languages of the Tribes in Xekong Province, Southern Laos
- Paul Sidwell (2005): The Katuic languages: classification, reconstruction and comparative lexicon
Sidwell (2005) reconstructs the consonant inventory of proto-Katuic as follows:
This is identical to reconstructions of Proto-Mon Khmer except for *ʄ, which is better preserved in the Katuic languages than in other branches of Austro-Asiatic, and which Sidwell believes was also present in Proto-Mon Khmer.
- Gehrmann, Ryan. 2016. The West Katuic languages: comparative phonology and diagnostic tools. Chiang Mai: Payap University MA Thesis.
- Gehrmann, Ryan. 2015. Vowel Height and Register Assignment in Katuic. Journal of the Southeast Asian Linguistics Society 8. 56-70.
- Gehrmann, Ryan and Johanna Conver. 2015. Katuic Phonological Features. Mon-Khmer Studies 44. 55-67.
- Choo, Marcus. 2012. The Status of Katuic. Chiang Mai: Linguistics Institute, Payap University.
- Choo, Marcus. 2010. Katuic Bibliography with Selected Annotations. Chiang Mai: Linguistics Institute, Payap University.
- Choo, Marcus. 2009. Katuic Bibliography. Chiang Mai: Linguistics Institute, Payap University.
- Sidwell, Paul. 2005. The Katuic languages: classification, reconstruction and comparative lexicon. LINCOM studies in Asian linguistics 58. Munich: LINCOM Europa. ISBN 3-89586-802-7
- Sidwell, Paul. 2005. Proto-Katuic phonology and the sub-grouping of Mon-Khmer languages. In Paul Sidwell (ed.), SEALSXV: Papers from the 15th Meeting of the South East Asian Linguistics Society, 193-204. Pacific Linguistics PL E1. Canberra: Pacific Linguistics.
- Theraphan L-Thongkum. 2002. The Role of endangered Mon-Khmer languages of Xekong Province, Southern Laos, in the reconstruction of Proto-Katuic. In Marlys Macken (ed.), Papers from the Tenth Annual Meeting of the Southeast Asian Linguistics Society. 407-429. Program for Southeast Asian Studies, Arizona State University.
- Theraphan L-Thongkum. 2001. ภาษาของนานาชนเผ่าในแขวงเซกองลาวใต้. Phasa khong nanachon phaw nai khweng Sekong Lao Tai. [Languages of the tribes in Xekong province, Southern Laos]. Bangkok: The Thailand Research Fund.
- Peiros, Ilia. 1996. Katuic comparative dictionary. Pacific Linguistics C-132. Canberra: Australian National University. ISBN 0-85883-435-9
- Miller, John & Carolyn Miller. 1996. Lexical comparison of Katuic Mon-Khmer languages with special focus on So-Bru groups in Northeast Thailand. Mon-Khmer Studies 26. 255-290.
- Migliazza, Brian. 1992. Lexicostatistic analysis of some Katuic languages. In Amara Prasithrathsint & Sudaporn Luksaneeyanawin (eds.), 3rd International Symposium on Language and Linguistics, 1320-1325. Bangkok: Chulalongkorn University.
- Gainey, Jerry. 1985. A comparative study of Kui, Bruu and So phonology from a genetic point of view. Bangkok: Chulalongkorn University MA thesis.
- Effimov, Aleksandr. 1983. Проблемы фонологической реконструкции прото-катуического языка. Probljemy phonologichjeskoj rjekonstruktsii Proto-Katuichjeskovo jazyka. [Issues in the phonological reconstruction of the Proto-Katuic language]. Moscow: Institute of Far Eastern tudies Moscow dissertation.
- Diffloth, Gérard. 1982. Registres, dévoisement, timbres vocaliques: leur histoire en Katouique. [Registers, devoicing, vowel phonation: their history in Katuic]. Mon-Khmer Studies 11. 47-82.
- Thomas, Dorothy. M. (1967). A phonological reconstruction of Proto–East Katuic. Grand Forks: University of North Dakota MA thesis.
- Hammarström, Harald; Forkel, Robert; Haspelmath, Martin; Bank, Sebastian, eds. (2016). "Katuic". Glottolog 2.7. Jena: Max Planck Institute for the Science of Human History.
- Lê Bá Thảo, Hoàng Ma, et. al; Viện hàn lâm khoa học xã hội Việt Nam - Viện dân tộc học. 2014. Các dân tộc ít người ở Việt Nam: các tỉnh phía nam. Ha Noi: Nhà xuất bản khoa học xã hội. ISBN 978-604-90-2436-8
- Sidwell, Paul. (2005). The Katuic languages: classification, reconstruction and comparative lexicon. LINCOM studies in Asian linguistics, 58. Muenchen: Lincom Europa. ISBN 3-89586-802-7
- Sidwell, Paul. (2009). Classifying the Austroasiatic languages: history and state of the art. LINCOM studies in Asian linguistics, 76. Munich: Lincom Europa.
- Paul Sidwell (2003)
- http://projekt.ht.lu.se/rwaai RWAAI (Repository and Workspace for Austroasiatic Intangible Heritage)
- http://hdl.handle.net/10050/00-0000-0000-0003-6712-F@view Katuic languages in RWAAI Digital Archive