Kutenai is a language isolate. There have been attempts to place Kutenai in either a Macro-Algonkian or Macro-Salishan language family, most recently with Salish, but these have not been generally accepted as proven.
Like other northwest languages, Kutenai has a rich inventory of consonants and a small inventory of vowels. However, there do exist other allophones of the three basic phonemic vowels. The lack of a phonemic distinction between voiced and voiceless consonants is much like other languages of the interior northwest. Due to Kutenai's location on the periphery of the northwest linguistic area, the loss of a rich lateral inventory is consistent with other interior northwest languages which today have only one or two lateral consonants. One such language group contains the Sahaptian languages which have had a similar loss of laterals. Nez Perce has /ts/ which was the lateral affricate in the proto-language. Nez Perce, like Kutenai, also lies in the eastern periphery of the Northwest Linguistic area. Another typological analysis investigates the lexical category of preverbs in Kutenai. This lexical category is distinctive of neighboring Algonquian languages which are located just on the other side of the Kootenay mountains, neighboring the Kutenai linguistic area. Another typological relationship Kutenai could have is the presence of its obviation system.
In 1991 Lawrence Richard Morgan wrote a description of the Kutenai Language as his PhD dissertation through the University of California, Berkeley. This description is focused on how the language works and specifically what are the working parts of the language. Morgan's work is an exhaustive list of each grammatical particle, morpheme, and affix with their respective environments and their varying forms.
Dryer, Matthew S (2002) A Comparison of Preverbs in Kutenai and Algonquian. In Proceedings of the Thirtieth Algonquian Conference, edited by David Pentland, pp. 63–94. Winnipeg: University of Manitoba.
Dryer, Matthew S. (2007) Kutenai, Algonquian, and the Pacific Northwest from an areal perspective. In Proceedings of the Thirty-Eighth Algonquian Conference, edited by H. C. Wolfart, pp. 155–206. Winnipeg: University of Manitoba.