There are significant differences between the Western and Eastern groups, which are sometimes counted as separate languages.

Joseph Greenberg grouped Keres with Siouan, Yuchi, Caddoan, and Iroquoian in a superstock called Keresiouan.

The great number of consonants relates to the three-way distinction between voiceless, aspirated and ejective consonants (e.g. /t tʰ tʼ/), and to the larger than average[4] number of fricatives (i.e. /s sʼ ʂ ʂʼ ʃ ʃʼ h/) and affricates, the latter also showing the three-way distinction found in stops.

Thus, a single vowel quality may occur with seven distinct realizations: /é è e̥ éː èː êː ěː/, all of which are used to distinguish words in the language.

The chart below contains the consonants of the proto-Keresan (or pre-Keresan) from Miller & Davis (1963) based on a comparison of Acoma, Santa Ana, and Santo Domingo, as well as other features of the dialects compiled from The Language of Santa Ana Pueblo (1964), Kansas Working Papers in Linguistics (1987), and The Phonemes of Keresan (1946), and the Grammar of Laguna Keres (2005).

The vowel chart below contains the vowel phonemes and allophones from the information of the Keresan languages combined from The Language of Santa Ana Pueblo (1964),[5] The Phonemes of Keresan (1946),[7] and Kansas Working Papers in Linguistics (1987).

There are phonetic grounds for vowel devoicing based on the environment they occur, for instance word-finally, but there are also exceptions.

[9] shdáurákụ 'frog, toad' shtérashtʼígá 'cricket' shtʼidyàatịshị 'plot of land' shjv 'upward' shchúmúmá 'wasp' shchʼísạ 'six' srbúuná 'water jug' srpàat'i 'mockingbird' srpʼeruru 'it's full' srgásrgáukʼa 'quail' srkv́dútsị 'mound, hill' srkʼabíhí 'female in-law' Traditional Keresan beliefs postulate that Keres is a sacred language that must exist only in its spoken form.

[12] The language's religious connotation and years of persecution of Pueblo religion by European colonizers may also explain why no unified orthographic convention exists for Keresan.

However, a practical spelling system has been developed for Laguna (Kʼawaika)[8] and more recently for Acoma (Áakʼu) Keres,[13] both of which are remarkably consistent.

Signs at Acoma Pueblo sometimes use special diacritics for ejective consonants that differ from the symbols above, as shown in the table:

Although Keresan is not normally written, there exists one dictionary of the language in which words are listed in any given order.

In this dictionary of Western Keres, digraphs count as single letters, although ejective consonants are not listed separately; occurring after their non-ejective counterparts.

The verb is a central grammatical category in Keres, conveying the most information about events in communicative acts.

Additionally, the person and number of the undergoer of the action are all coded on the verb (e.g. the word gukacha means “S/he sees her/him”, a full sentence in English).

39–40)[10] In Keres, the verbal prefix carries information from five different grammatical categories: argument role, modality, polarity,[8] person and number.

The plural and dual forms are often marked by reduplication of part of the stem (gukacha ‘s/he saw it’ vs guʼukacha ‘the two of them saw it’).

to leave (-mi), to whistle (-srbiitsa), to sweat (-shdyuwàan’i) to be afraid (-tyishu), to forget (-dyúmidruwi) Ideas expressed in Indo-European languages with adjectives are most often encoded by verbs in Keresan.

Numerals 20 and above are formed by adding a multiplicative adverb (-wa or -ya) to the base number and the word kʼátsi.

[8] European colonizers arriving in the Southwest US brought with them material culture and concepts that were unknown to the peoples living in the area.