The Kiliwa language was extensively studied by Mauricio J. Mixco, who published Kiliwa texts as well as a dictionary and studies of syntax.
As recently as the mid-1900s, Mixco reported that members of the native community universally spoke Kiliwa as their first language, with many Kiliwas also bilingual in Paipai. At the start of the twenty-first century, Kiliwa is still spoken; a 2000 census reported 52 speakers. However, the language is considered to be in danger of extinction.
Kiliwa is a language of the Yuman Family Language Summit, held annually since 2001.
Kiliwa is the southernmost representative of the Yuman family, and the one that is most distinct from the remaining languages, which constitute Core Yuman. The Kiliwa's neighbors to the south, the Cochimí, spoke a language or a family of languages that was probably closely related to but not within the Yuman family. Consequently, the Kiliwa lie at the historic "center of gravity" for the differentiation of Yuman from Cochimí and of the Yuman branches from each other.
Linguistic prehistorians are not in agreement as to whether the Kiliwa's linguistic ancestors are most likely to have migrated into the Baja California peninsula from the north separately from the ancestors of the Cochimí and the Core Yumans, or whether they became differentiated from those groups in place. The controversial technique of glottochronology suggests that the separation of Kiliwa from Core Yuman may have occurred about 2,000-3,000 years ago.
Intervocalic allophones of /p, t, k, kʷ/ can occur as [β, ð, ɣ, ɣʷ]. An approximant sound such as a /j/ sound after a glottal /h/ can become devoiced as [j̊], as with a devoiced [w̥] sound being an allophone of /hʷ/.
There are three vowel quantities; /i, u, a/, that can also be distinguished with vowel length /iː, uː, aː/. Close vowel sounds /i, u/ can range to mid vowel sounds as [e, o], and with vowel length as [eː, oː]. An epenthetic schwa sound [ə] can occur within root-initial consonant clusters.
(1) High level, (2) High-falling level, (3) Low level.
The morphology in the Kiliwa language consists of many affixes and clitics. More of these are available on the verb rather than the noun. These affixes are usually untouched and added on to a modified root.
Kiliwa is a verb-final language that usually follows the order subject-object-verb. Dependent object clause should be found before the verb, whereas relative or adjectival clauses appear to the right of the noun they modify.
The following Kiliwa toponyms are from the map given in Mixco (2000:70).
- xaʔ kwpan - Agua Caliente
- xpiʔ kwnaan - San Isidro
- mxwaa - Los Coches
- pnyil - Santo Domingo
- kwʔiy yuwuʔ - San Quintin
- xwiym xaʔ - San Felipe
- ʔipaʔ cʔaa - Tijuana
- xwa nymat - Mexicali
- xaʔtay hwatuʔ - Ensenada
- yuwl ʔmat - Santa Catarina
- Natural features
- kwʔiy yaquʔ - Salinas
- xyil - Cañón de la Esperanza
- xyaaw - San Matias Pass
- kwmsalp - Colnett Point
- ʔmuw wiiy - Cerro Borrego
- nyaay wiiy - peak just to the south of Cerro Borrego
- muw waʔ wiiy - Cerro Salvatierra
- ʔqhaay spkwin - peak just to the south of Cerro Salvatierra
- mt waay walu wiiy - Picacho de Diablo
- ʔxaal haq - Sierra de San Pedro Martir
- kwnyiil wiiy - Cerro Colorado
- Bodies of water
- "Kiliwa language in danger of extinction in Baja California". Veraz Informa (in Spanish). Retrieved 2018-05-11.
- Hammarström, Harald; Forkel, Robert; Haspelmath, Martin, eds. (2017). "Kiliwa". Glottolog 3.0. Jena, Germany: Max Planck Institute for the Science of Human History.
- "Yuman Language Family Summit Home Page". Retrieved 2012-09-22.
- Mixco, Mauricio J. (2013). Introduction to the Kiliwa Language. Department of Linguistics, University of Utah.
- Mixco, Mauricio J.. 1971. Kiliwa Grammar. Ph.D. dissertation, Department of Linguistics, University of California, Berkeley.
- Mixco, Mauricio J.. 1976. "Kiliwa Texts". International Journal of American Linguistics Native American Text Series 1:92-101.
- Mixco, Mauricio J.. 1977. "The Linguistic Affiliation of the Ñakipa and Yakakwal of Lower California". International Journal of American Linguistics 43:189-200.
- Mixco, Mauricio J.. 1983. Kiliwa Texts: "When I Have Donned My Crest of Stars" University of Utah Anthropological Papers No. 107. (Myths and legends narrated by Rufino Ochurte and Braulio Espinosa after 1966.). Salt Lake City.
- Mixco, Mauricio J.. 1985. Kiliwa Dictionary. University of Utah Anthropological Papers No. 109. Salt Lake City.
- Mixco, Mauricio J.. 1996. Kiliwa de Arroyo León, Baja California. Archivo de Lenguas Indígenas de México No. 18. Mexico City: Colegio de México.
- Mixco, Mauricio J.. 2000. Kiliwa. Munich, Germany: Lincom.
- Mixco, Mauricio J.. 2006. "The Indigenous Languages". In The Prehistory of Baja California: Advances in the Archaeology of the Forgotten Peninsula, edited by Don Laylander and Jerry D. Moore, pp. 24–41. Gainesville: University Press of Florida.
- Moore, Jerry D.. 2006. "The San Quintín-El Rosario Region". In The Prehistory of Baja California: Advances in the Archaeology of the Forgotten Peninsula, edited by Don Laylander and Jerry D. Moore, pp. 179–195. Gainesville: University Press of Florida.
- Ochoa Zazueta, Jesús Ángel. 1978. Los kiliwa y el mundo se hizo así. Mexico City: Instituto Nacional Indigenista,