The people are called "Luiseño", owing to their proximity to the Mission San Luis Rey de Francia.

Overlong vowels are rare in Luiseño, typically reserved for absolutes, such as interjections, e.g. aaashisha, roughly "haha!"

For some native speakers recorded in The Sparkman Grammar of Luiseño, the allophones [ə] and [ɨ] are free variants of [e] and [i] respectively.

However, some take a glottal stop instead: ch [ʔt͜ʃ], kw [ʔkʷ], qw [ʔqʷ], ng [ŋʔ], th [ðʔ], v [vʔ], x [xʔ] (Elliot 1999: 14–16.)

One rare exception is the word pó-ha "alone" (< po- "his/her/its" + ha "self"), whose invariable prefix and fixed accent suggests that it is now considered a single lexical item (compare noha "myself", poha "him/herself", etc.).

Although Luiseño has no standardized spelling, a commonly accepted orthography is implemented in reservation classrooms and college campuses in San Diego where the language is taught.

The various orthographies that have been used for writing the language show influences from Spanish, English and Americanist phonetic notation.

Luiseño is an agglutinative language, where words use suffix complexes for a variety of purposes with several morphemes strung together.