Zapotec phonetics and phonology

Fortis / Lenis
In Zapotec languages, fortis typically corresponds to voicelessness and extra length in obstruents and extra length in sonorants. Lenis corresponds to voicing and less length in obstruents and less length in sonorants. In addition, stressed vowels before lenis consonants may be longer than those before fortis consonants.

Retroflex consonants
Some varieties of Zapotec have a contrast between alveopalatal fricatives and retroflex fricatives. In other varieties this distinction has been lost in favor of only one or the other.

Tone
Zapotec languages are tonal, as are Otomanguean languages generally. Unfortunately, materials on Zapotec languages vary widely in the quality of their tonal description and analysis.

Many Northern Zapotec languages, such as Sierra Juárez (Nellis and Nellis 1983, Bickmore and Broadwell 1998, Tejada 2010) show a system of three level tones (L, M, H) plus two contours. Potential aspect and 1st person singular both involve floating high tones. One example is Texmelucan Zapotec, which has four contrasting tones: three contour tones and one level tone, as shown in the figure. These tones are used for "word play" frequently.

A typical system for a Central Zapotec language has two level tones plus contours, but there are complex interactions between tone, stress and phonation type, e.g. San Lucas Quiaviní (Chávez Peón 2010).

Phonation
Zapotec languages all display contrastive phonation type differences in vowels. Minimally they have simple vowels vs. some kind of laryngealization or creakiness; see Quioquitani Zapotec, for example. Others have a contrast between simple, laryngealized and "checked" vowels (which sound like they end in a glottal stop); see Isthmus Zapotec, for example. Others have a contrast between those types and also breathy vowels. The latter varieties include Mitla Zapotec and San Lucas Quiaviní Zapotec.

Stress
Varieties that are described as having stress, including Isthmus Zapotec, have it on the penultimate syllable of the root. Prefixes and clitics do not affect it. Many varieties overwhelmingly have monosyllabic roots and stress falls on that syllable.