Seri phonology

Vowels
Vowel length is contrastive only in stressed syllables. The low front vowels are phonetically between open-mid and near-open, and have also been transcribed as.

The non-rounded vowels may be realized as diphthongs  when followed by the rounded consonants, but this small phonetic detail is not written in the community-based writing system.

Consonants
occurs only in loanwords. occurs in loanwords and in a few native words, where it may alternate with depending on the word and the individual speaker. Other consonants may occur in recent loans, such as in hamiigo ("friend" from Spanish amigo), and  in hoova ("grape" from Spanish uva).

The labial fricative may be labiodental  for some speakers, and the postalveolar fricative  may be retroflex.

In unstressed syllables, assimilates to the place of articulation of the following consonant. This assimilation may take place over word boundaries in connected speech. When is preceded by  or, it becomes a nasalized approximant  and the following vowel becomes nasalized, e.g. cmiique  "person; Seri" is pronounced  or. For some speakers, word-final may become  at the end of a phrase or sentence, or when said in isolation. It can be documented, by careful examination of word lists collected in the nineteenth century, that some of these phonetic rules have arisen fairly recently.

Phonotactics
Seri generally allows up to three consonants to occur together at the beginning or end of a syllable. It is like English in this respect, which allows three-consonant combinations like spray and acts. Unlike English, however, the specific combinations which may occur are much less restricted. For example, English allows spr- but disallows *ptk-, which Seri does allow, as in ptcamn, ("Cortez spiny lobster", Panulirus inflatus).

Rarely, clusters of four consonants can occur, e.g. in cösxtamt, ..., "there were many, ...";  in ipoomjc x, ... "if s/he brings it, ...", (with enclitic x)

Stress
Stress is contrastive in Seri. Although it usually falls on the first syllable of a root, there are many words where it does not. These are mostly nouns, as well as a small class of common verbs whose stress may fall on a prefix rather than on the root. An alternative analysis, recently proposed and with fewer exceptions, assigns stress to the penultimate syllable of the root of a word (since suffixes are never stressed and prefixes receive stress only as a result of phonological fusion with the root). This rule is also sensitive to syllable weight. A heavy final syllable in the root attracts stress. A heavy syllable is one that has a long vowel or vowel cluster or a final consonant cluster. (A single consonant in the syllable coda is typically counted as extrametrical in Seri.)

Consonants following a stressed syllable are lengthened, and vowels separated from a preceding stressed vowel by a single consonant are also lengthened, so that e.g. cootaj ("ant") is pronounced. Such allophonically lengthened vowels may be longer than the phonemically long vowels found in stressed syllables. This lengthening does not occur if the following consonant or vowel is part of a suffix (e.g. coo-taj, the plural of coo ("shovelnose guitarfish"), is, without lengthening) if the stressed syllable consists of a long vowel and a short vowel (caaijoj, a kind of manta ray, is , without lengthening), or if the stressed vowel is lengthened to indicate intensity. It also doesn't affect most loanwords.