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 (2003). 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.
- Pacoh language (Tareng) (Vietnam and Laos)
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.
- 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, P. (2005). The Katuic languages: classification, reconstruction and comparative lexicon. LINCOM studies in Asian linguistics, 58. Muenchen: Lincom Europa. ISBN 3-89586-802-7
- Sidwell, P. (2005). Proto-Katuic phonology and the sub-grouping of Mon-Khmer languages. SEALSXV: Papers from the 15th Meeting of the South East Asian Linguistics Society. Canberra, Pacific Linguistic. pp. 193–204
- Peiros, I. (1996). Katuic comparative dictionary. Canberra, Australia: Dept. of Linguistics, Research School of Pacific and Asian Studies, Australian National University. ISBN 0-85883-435-9
- Migliazza, Brian Louis. (1992). Lexicostatistic analysis of some Katuic languages. Proceedings of the Third International of Language and Linguistics, vol.3 pages 1320-1325. Bangkok: Chulalongkorn University Printing House.
- Costello, N. A. (1991). Nôôq paraaq Katu: Katu dictionary : Katu–Vietnamese–English. Manila: Summer Institute of Linguistics, Thailand Group.
- Thomas, D. M. (1976). A phonological reconstruction of Proto–East Katuic. Grand Forks, N.D.: Summer Institute of Linguistics.
- 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.